Your odds are not very good with a broken tap root. This is a frequent problem in transplanting trees from the wild (the smallest trees (actual seedlings and not root suckers) have the best chance of surviving transplantation).

Supposedly sassafras can also be grown from root cuttings. I'd be interested to hear from anyone who's done this successfully.

There's nothing magical about a taproot. While they do provide some anchorage, their major purpose is to serve as a storage receptacle for fueling the next year's start-up growth - or reserves in the even some calamity befalls the above ground portion of the seedling(encounter with a mower, weedeater, browsing deer, rabbit, etc.). Therefore, when digging and transplanting any taprooted species, it's best to preserve as much taproot as is possible, but severing the taproot is not an automatic 'death sentence'.
Sassafras is notoriously difficult to transplant - for whatever reason, I don't know - but it is; At this juncture, all you can do is wait and see. Some species prefer late winter/early spring transplanting, while others are favored by early fall digging and transplanting; I don't know which camp(if either) sassafras falls into.

"Magical" or not, preservation of an intact tap root is cited by numerous authorities as important in the survival of transplanted sassafras trees.

From Floridata: "It is difficult to transplant sassafras since it has a very long tap root."

Texas A&M: "Because it has a tap root and sparse spreading roots sassafras is difficult to transplant from the wild."

carolroses' tree may or may not survive, but the odds are against it. I've lost a sassafras transplant under similar circumstances.

I sure would like for someone to explain to me how to transplant a tree with an "intact tap root".
When I dig a rootball I use a sharp spade, form the rootball and sever the roots as I go. I put the burlap on while still in the hole and if the tree is big enough I lace it up with twine.
You can't possibly dig a tree without pruning the roots. Did you ever work in a packing shed in the winter? Even bareroot seedlings have roots cut back on chopping block.
Sassafras dug from the wild will have a straggly root system just like the quote from Texas A&M says, because they have never been transplanted.
It's not rocket science, every time you transplant a tree, the root system improves and is less coarse.
Sam

My point exactly, Sam; it's virtually impossible to dig a seedling of any size without losing some root mass.
I wasn't attacking Eric's post, just trying to debunk the myth I see put forward frequently that "if you cut the taproot, the tree will die". More and more commercial nurseries are root-pruning/undercutting their taprooted species during the first or second growing season, in order to promote development of a more lateralized root system, which translates into a higher transplant survival rate.

I've dug and transplanted thousands of strongly-taprooted seedlings - pecans, walnuts, hickories, oaks - and sometimes these have been 3, 4, 5-yr old seedlings, frequently taller than myself. I certainly try to preserve as much taproot as is possible, but occasionally, due to close spacing in the seedling beds and unexpected root orientations, these trees come out with less than 1 ft of intact taproot. Most survive quite nicely, in spite of it.

Again, season of digging/transplanting may have a significant impact. For example, another 'taprooted' species, the pawpaw, is very different from most other North American deciduous tree species, in that it carries out virtually no root growth during the dormant period - once it goes dormant, every part of the plant is dormant; so...when digging and transplanting pawpaw seedlings, the best time to do so is in spring, just as they're breaking dormancy, or in late summer, before they begin the descent into fall dormancy.

Lucky,
I have found your posts to be consistently accurate and its clear that your observations are based on first hand observation and experience.
Sam

I'm very interested reading all the responses, and can't wait until Spring to see if this tiny object of discussion decides to live. It's been cool here with lots of rain, so I'm hoping that may help.

My experience also confirms Eric's position. Even babied Sassafras (note correct spelling) transplants with tap root damage are much less likely to survive.

All Sassafras transplants I have seen at nurseries include an intact taproot. Many even have a tag advising extreme care with the taproot when planting. These trees are grown in a very loose media so that they can be extracted without damaging the roots.

The taproot is much less important on some types of trees, but trees like Sassafras and Asimina (pawpaw) have a much better chance of survival with their taproot intact.

If they weren't such a weed here - though I do like the fall color display, and even the spring blossom show - but not enough to put one in my YARD! - I'd try my hand at digging and transplanting a few just to see if I could get 'em to survive.
I pulled some 2-3-leaf seedlings out of the potted figs this spring, and stuck them in some small 4" pots. I think - I haven't looked lately - 3 of 4 survived.

If trees whose taproots are really important get their taproots severed, would it make sense to fertilize and water these more than most others, for at least the first year?

I planted a couple pawpaws a year ago. I noticed when I took them out of their pots that their taproots were severed. They've been growing okay this summer.

I just wanted to update the world - my sassafras lives!! It held the tiny buds all winter and they've just started leafing out. It's so wonderful, and I hope it continues to do well. I put it in an area that can take some spreading, should any suckers come up around it. I have lots of wild areas around my property, and it's at the edge of one, but an area I frequent. Thanks to everyone for their help and advice.

That's wonderful!
I can imagine that sassafras would be very difficult to successfully transplant from the wild. It grows all over my property and is the biggest "wanderer" here, apparently mostly from root suckers, although I do see very small plants that look like seedlings, growing pretty much alone. I guess they start the whole process over again!
Sassafras is one of the two main host plants, along with spicebush, for spicebush swallowtails - if you see any leaf rolls and peek in, you might see a caterpillar with "eyes" - it'll become a beautiful butterfly!
Sherry