Originally Posted by PR_Tom

Of course your thank you's should be enough. People should return things when found, it's the normal thing to do, in every generation.

I wouldnt treat it like he was a hero, or else it sends the message that simply doing the correct thing is somehow extraordinary. The news is constantly guilty of this.

I would thank him profusely which you have done, and probably offered to buy lunch or something and let him accept or decline on the spot as well. It's also the normal, nice thing to do.