Of course the owner thanked me, although he didn't really look as though I did any favor for him.
Which is a major reason why most people wouldn't have even bothered trying to return it. You went out of your way to make sure this guy got his expensive phone back, and he was basically indifferent about it.
I would have offered you a beer or something, at the very least. In any case it sounds like you did it because it was the right thing to do, rather than hoping for a reward or recognition anyway... a commendable trait.