damn dude. that's a nightmare. do you have a bubble cloner? if you do, thats's the only thing i can think of to save it, maybe try replanting it and giving it a little TLC, give it a fighting chance by just babying it. i dont know what else to suggest, someone who knows more please help?
ive learned from experience that your babies will try very fuckin hard to survive. if the plant isnt totally dead try to save it
dont feed it. if you have a little spray bottle, try to keep the soil around it moist but dont spray the seedling itself. if its still alive it will reroot itself. my cat knocked one of my seedlings off just the other day and i rescued it from the floor planted it and its recovering. its turned from brown to yellowish green. it was a day old had just cracked its shell no leaves open yet. and it still survived...
I think geheim is on the right track. Put some rooting hormone on what is left of the roots, plant it. Maybe put it in a dome to preserve moisture. Basically treat it like you are cloning it. And pray to whatever higher power you belive in.