Yes, that florist wants you to buy another tree because your cal will surely die on his advice. I killed my mature cal (over 15 years old) on the ground that way. It's along story but I even put a sprinkler system that will go on twice a day until finally when it died I dug it and the soil smelled like a sewer. It tried to survived itself but the constant watering it finally gave up.
It maybe too late once all the root rotted.
The main thing is to kill all the fungus that are living in your root system.
I think you will have to take it at your house and do it from there. Do you have a yard?
You'll have to take your plant out of the pot and inspect the roots.
If you find that the roots are rotted cut the ones that are rotted and mix about 5 % clorox to a warm big bucket of water. Dip the roots there for about 5 minutes then flush the chlorox out with another warm water.
Before this prepare a new potting mix well drained soil maybe 1/3 sand 1/3 peat and 1/3 potting soil.
Cut the top branches off and the sides if you must maybe 1/3 of the tree specially the new young leaves. I mean drastically because of the lost roots.
Then soak the soil till it is really soak but you'll notice the water will stay on top less than 7 seconds. Let all the water out.
Then put it in a shade until you find new buds start sprouting.
Do not put fertilizer till new sprouts comes out .then read the thread below how I advice doing it.
Water only till the 1st 2 inches of soil is dry to the touch. Do that always.
If you think that the roots are not rotted then just transfer it toa next bigger pot, still remove as much old soil but try not to disturb the roots and transplant. Still you do the above putting the plant in the shade etc...
Also the plant needs some humidity without water in the air the plant will lose its leaves.
Good luck.
Your plant is in a state of shock.

I reread and reread your concern about your cal. It might still recover if you just stop watering your plant and let it just sit where it is now. It may not have root rot yet. Just let the soil dry up up to 2 inches of your top soil from now on.

One thing I learned is NEVER listen to ppl/clerks who work for florists including ppl from Home Depot..they know not the truth.
As Ben stated, this clerk may want you to buy another tree..it's possible.
She'd best read up on plants before commenting to people..
In the futre, I'd either come here, or read articles online before jumping the gun.
The soil should dry between waterings. I don'tknow if it's too late for your plant, but from now on, let soil dry. Remove bad leaves or dead braches. Fertilize when plant resumes health.
Make sure it's getting proper humidity and fresh air. A humidifer and fan will help.
There is a product called Superthrive that is used for stressed plants..I'd look into buying a bottle. You can even get a free sample on their site, www.superthrive.com ..Give it a try and see how your plant does.
Mist leaves daily, but make sure the soil dries..When u do water, you want to do so thoroughly..water all parts of the rootball, until water seeps out of the drainage holes..Oh and use a pot that has drainage holes.

Keep the plant in bright light. If you feel there's a drainage problem, then maybe it's best to repot..
What size pot is your tree in? If you repot use a well-draining soil. I only hope the soil they used was well-draining as well. You don't want roots sitting in constant water. Good luck, Toni

If it's lost so many leaves and branches are dying, I'd bet there is some root rot.
Re-pot as soon as you can, removing as much of the old soil as possible, and use a good, well-draining potting mix. Make sure to layer some small stones or pebbles in the bottom of the new pot before adding soil, to help drainage and to make sure that the roots aren't sitting in water collected in the saucer (I'm assuming you have one so that the office floor isn't ruined.) Remove any fruit and flower buds so that the plant's energy isn't put into them, but instead into recovering.
I'm wondering if your office really is bright enough for a citrus? That might have led to the initial leaf drop, perhaps? I have a fairly bright window in my office, but I know it won't sustain a citrus.
I grow several types of citrus in containers in NJ, including a calamondin. They are outside getting 8 hours of direct sun during spring and summer, and I overwinter them in a cool sunroom. They thrive and have masses of fruit each year. The calamondin is the least tempermental one I have and I let the soil dry between waterings almost to the point of wilt (and sometimes it has when I'm negligent). They like humidity, but not wet soil--I give them a misting when conditions are dry.

There are many florists that know how to arrange flowers and plants, but know nothing about actually growing and caring for them. I've been in the position you are and that's why I don't trust anyone anymore -- I find it's best to find authoritative sites on the web when I get a plant I'm unfamiliar with. Not every florist or Home Depot clerk is clueless, but chances are...and the employees at my local Smith & Hawken are even less knowledgeable about the plants they sell (don't get me started...)
I guess it's too late to ask for a replacement, but it's a shame since she supplied you with misinformation, so it wasn't your fault, really.

I wish you the best of luck--please give an update on how things turn out.

CAl, which direction sun is your citrus getting? That's terrrible if it was receiving little light, and you've been overwatering.
I agree that you should repot in fresh, dry soil. Then water the correct way..I hope you dont' lose this tree cause it sounds nice.
I can't believe that clerk told u to water every couple days. I'd report her for sure..she doesn't know what she's talking about. She should NOT be giving advice on caring for plants. Especially citrus.
I'd call and *itch her out for sure. She wasn't being helpful, on the contrary..A 5' cal is an expensive plant..I could imagine what it cost..Maybe she expects you to buy another..who knows what's in the minds of men. Toni