You will be fine! I do this occasionally, and can't always find (or remember) which voucher I held a certain reservation with. So I just send in whichever voucher I can find.

Then I invariably get a panicked phone call from AA a few days later, when they receive the voucher. They're concerned that it's not exactly the same amount. I just explain that I couldn't find the correct voucher when I mailed it in. So they give me the new amount that will be charged to my CC, or refunded in the new voucher, and we're all set.

And no, the voucher doesn't need to be in your name.