What if no one came looking for that bill? What is the manager gonna do? just keep it?
Indeed. That's how bribes tend to work. "Oh, no, I wasn't bribing him, you see, I just found this money on the ground, and I thought I'd give it to him for safekeeping... he seemed like the right person to give it to. I mean, someone might have stolen it! And any favours he did for me after were pure coincidence..." Even if you weren't /intending/ to receive a favour, you were opening the opportunity. And the teller has no official (laws in your region may vary) duty to handle lost property on behalf of third parties.
If you find some lost property, you could hand it to the owner, or report to the police. A distant third is to try a lost property department if at some public place, e.g. airport. Anything else is pretty much equivalent in terms of having decided that you're not interested in having the owner get it back.
If you'd identified this phone as almost certainly an Apple prototype, it was absolutely the correct thing to do to contact Apple. Which was done. And if Apple had abandoned the property, because someone speaking on behalf of Apple wasn't aware of what it was, well, sucks to be Apple. Which is what happened. It doesn't matter that Joe Developer had the phone on his person - it wasn't, as far as anyone seemed to believe, actually his property.
So, everyone's out to make a buck, everyone's incompetent, everyone's self-righteous, and everyone's blaming everyone else. And the world's best marketing company is enjoying the world's best marketing. Business as usual.