Did you borrow a phone and try calling/texting your number? I actually did find and return a phone once when a text came through and I arranged to meet the person at a public place to return it.
I'd give it back happily.. but I think I would have to wait until they tried to call the number as I am not sure I could get into the phone with all the security codes etc.
Oh, CMI! I'm sorry to hear that you lost your phone. I hope someone finds it and returns it to you.
To answer your question: Absolutely. As a matter of fact, it doesn't matter what kind of phone it is, I would make every effort to track down the owner. I've found a wallet and a few purses when I used to ride the train on a daily basis. It wouldn't enter my mind not to attempt to find the owner.
Adaydreambeliever 