If WIn 7 there will probably be a GUID on the disk you can view with the "mountvol" command. I don't remember on a Windows system how to get a history of the GUID of the drives you have connected in the past, but they are probably in the registry.
If Linux it's trivial but need to know if you're using it or not before I dig up the man pages. :-)
Is there any sticker on USB drive with numbers on it?. If there is numbers exist on the sticker you can compare those numbers with the numbers on the bill you received when you bought the USB drive.That way you can identify your drive.
You can use a program called PhotoRec and/or testdisc to retrieve all the previous data that had ever been stored on the USB stick to ensure it is yours, if your planning to just return it i cant help.
I have used this program a few times before, last time i used it on a 4gb flash drive, i retrieved 12gb worth of data it was a random one i had found in my house but it was empty, after getting all that data i found out who's it was, i returned it to them and they where a bit shocked that all that information was still on there from years and years ago.
If you want to protect your identity format often!
I tested this on a friends 2gb flash drive, found out their bank details, their work roster, their old address and new one, they where horrified. Very powerful tool i love it.