It is considered a rare side effect of vyvanse, but definitely listed as one. Many people are reporting this as well, (online) as a result of taking the medication. It may just be listed as rare due to the fact that people may not have realized during clinical trials that their hair loss was a direct effect of the medication. I know that I have experienced many "rare" side effects from medications, hence why I don't always believe they are as rare as early trials may have reported. But I do agree, you should definitely talk to your doctor.
I'd see your MD, but unexpected hair loss can be due to stress amongst other things, the condition is called alopecia areata. I'm not sure hair loss is an adverse effect of Vyvanse is it?
Since this is a side effect of the medication and you are unable to stop it while in college, I'll give you a tip on concealing thinning hair. I am in my 30's and as you know, being female and caring about your hair go hand in hand. I use Suave dry shampoo to make the hair appear thicker. My forehead area has noticeable thinning and you can see right through to the scalp. The dry shampoo makes each strand appear thicker therefore covering my bald spots, per say. I do have dark blonde hair though... not sure how brown or darker hair would respond. Also, I've tried every brand out there including the expensive ones and Suave is definitely the best. Good luck and hope this helps.