This needs a follow up! good luck on your situation op!

Purchase a pen

After you get your grades back, don't forget to punch that bastard in nose.

Have you not been checking your grades when they are posted? That should've told you earlier in the semester. Either way, that sucks

What a goddamn rat, ask the teacher to compare your writing. This should have serious academic ramifications.

OP I want an update on this!!

If this is a college class contact the dean and security. They can get some serious charges pressed on the TA that stole your work

Most colleges have strict rules against stealing work. File charges. You should be able to prove it was your work with computer records, etc. Even if not once charges are filed you can ask for them to test you and the TA. Your fingerprints should be all over the paper that was turned in. If that does not work threaten court. You paid for the course, and spent countless hours on the work. If the TA stole your work and you fail the course that qualifies as theft. As it is probably a very significant amount (tuition, housing, hours of work, etc.) it probably qualifies as a felony. Since the TA was technically an employee of the school, you would name the school as well as the TA in the suit. My guess is that they just want to ignore it as a problem, but if they get a letter from a lawyer it becomes a much bigger problem. (Hire a lawyer - it gives credence to your willingness to fight this). They want to avoid court and the bad publicity (imagine it getting out in the news). They would probably me much happier to start looking into the case at this point.

TA is teacher's assistant. Someone in the education program shadowing a class. Although I don't know how that's allowed that she is also in it....

You should definitely go to the teacher and if need be over their head. On another note, how is the TA someone who hasn't actually taken the class?