There's no picture on your post.

Only one picture can be attached at a time. It must be reattached every time the post is edited until final submission. It won't be on the submitted post if it isn't seen on the preview.

trying again to post the photo

How old is your refrigerator? Is it still covered under the Samsung warranty? If you are unsure, review Samsung's warranty info on their website. If so, I'd suggest calling Samsung asap and getting them to send one of their authorized service providers to look at it. Perhaps Lowe's fits that description, IDK. I had a french door refrigerator develop an unrepairable sealed system leak while it was under still under warranty and while eventually Samsung did refund my purchase price, it was an uphill battle with them for a while.

Most warranties do not cover cosmetic issues. If they fixed the drain clog, then that's all that is covered. If you bought an extended warranty, some do and some don't cover cosmetic issues.

Just clean that with some Oxyclean and hot water and while it won't completely get the stain out, it will look better.

Maybe something was spilled and ran down the panel?

Or, it could be sealant of some ilk from the factory.

If the unit is cooling and defrosting, working properly as you say, then ignore the gunk. It's on back of the evaporator cover panel, yes? ... so you don't see it under normal conditions.

A refrigerant leak from the evaporator shouldn't generate such residue ... Freon or other refrigerant would emanate from a leak as an invisible gas, not a liquid.

Get a replacement panel if it's really bothersome to you.

The refrigerator is 3 years old. My concern is the cause and then next year's future damage, if any, when I am not covered. I am under a 5 year warranty with Lowes. They sent out a serviceman who said "I can't fix that" and that was that. He also told his main office that I had some 'rust from some screws'.
I can't see the problem with the panel in place so cosmetics are not my concern. I just want it to be fixed, if it needs to be, so I won't have problems in the future if it could cause problems. Since I don't know where it is coming from, I don't know how to proceed.

Your pictures are close-ups, difficult to orient where is the residue in relation to the unit as a whole ... what's the apparent source and how far it extends, what all it covers.

Appears to be a styrofoam insulation panel in the pic immediately above ... ?

Really, it seems (based on the pictures) to me that something spilled in the freezer and ran down behind the panel. Maybe it's rust but rust is usually more reddish. Your residue is brownish and black.

Is it sticky?

Lowe's tech is saying he can't fix it because, as you say, there's nothing apparently wrong with the functioning of the refrigerator, and they're not going to replace panels and parts for a cosmetic issue, the warranty likely doesn't provide for it.

First of all- they've made 2 service calls already. Call the store you purchased it from and speak with the manager. Our ice maker quit. Took forever for them to "find" the warranty, then they sent a repair man who replaced it and the control panel. Worked for about a week. Sent another repair man who said it was our water pressure. Since it had worked before, then with the new ice maker, I didn't buy it. I called and it was escalated to the local store. They ended up replacing the fridge (like yours, 3 years old), I upgraded to a counter depth, they price matched one on sale at Best Buy (plus additional 10% off). Walked out with a new fridge, delivered with another new warranty for $81- that included tax and a new stainless steel water line. I have NO clue how I got out of there so cheap- asked them 3 times if they were sure of the price- considering the 1st was about $500 cheaper to begin with.

Well, could it just be a spill? If you are concerned that the residue is being caused by an undiagnosed problem, then pay the $90 to have them take another look, or call another company to do the same. Is it correct that when they told you it couldn't be repaired, they were talking about the stain itself and not some issue causing ongoing staining?

This is the 3rd photo and the last one I have. The picture is the panel behind the interior back panel which was removed to fix the drain. If there is something coming from the silver foil (can you see that?) what would that part be? Does anyone know? I have tried to put up another photo. The refrigerator is working and I will need to look at a detailed copy of my Lowes' 5 year warranty to see if it covers cosmetics - and I notice now I never received a detailed copy -just a receipt. Nothing spilled from the inside and the freezer is on the bottom.

My opinion without having hands-on access ... adhesive oozing from the foil shield.

Is it sticky? Does it have "thickness" and dimension as if something has oozed down?

Once he put the back panel back on, I no longer have access and only have the photos and my memory. I seem to recall the stain was not flat and in the first picture above I think you can see it isn't flat.

OK, that supports that it's probably adhesive oozed/seeped from the foil, which is to shield the interior liner against direct heat exposure from the defrost element which is mounted under the evaporator coil. Or maybe a worker on the production line got sloppy when installing the foil piece.

Where does the defrost condensate route? Do you recall if there's a drainhole in the foil directly under the coil?

I had the same issue with my old Westinghouse. I simply cleaned it off and checked it again a month later to see it had come back. Nothing to worry about.

I don't recall the drain hole. Maybe I should get a repairman/handyman to clean it off and then look again in a month or so. Samsung says $90 to ring my doorbell. Lowes never gave me a detailed sheet so I also need to check and see if my 5 year warranty covers cosmetic damage. Thanks for your help. Somehow about a year ago, answers used to get to my email and they no longer do??????

I finally talked the warranty folks from Lowes to come back w/o a charge and (please) send someone who knew something. He took the interior back panel off and sure enough more rusting. The culprit was the drain which somehow was allowing the water to splash forward against the panel and thereby continuously rust. There does seem to be a problem with the Samsung drain (according to three repairmen). Repairman is going to adjust the level of the drain, etc. and should no longer be a problem. Thanks for all the answers I received.