A while back I lost a flash drive during a road trip. Amazingly, someone found it, contacted me, and offered to return it--even going so far as to cover the cost of postage. (Who says there are no good Samaritans?)
The embarrassing part is that she obtained my e-mail address by digging through various documents on the drive. Nothing mission-critical, mind you, but I wished she'd had an easier (and less-intrusive) means of finding me--like, say, a simple, easy-to-spot text file with my contact info.
Here's what it says inside the file: "You found my flash drive! Thanks a million for being honest and returning it to me. Please call me at [phone number] or e-mail me at [e-mail address]. There's a reward waiting!"
Offering a reward is optional, of course, but I think a $5 Starbucks card (or equivalent) would be the perfect gesture for something like this.
Certainly there's no guarantee this will help you recover a lost drive--but I think it'll improve your odds considerably. At the same time, consider slapping on a "found me" sticker like the ones offered by SendMeHome.