Did you trace their IP address to be sure it isn't someone outside the area screwing with your heart strings? There are always trolls... I'm hoping desperately this is not the case, but most IP address in US can be traced to the same city the person lives in, often within a mile or a few blocks (if its a large city as I think you mentioned).
It wont give you the extra address, but it will at least tell you they're not located out of state or something.
I would email the person who sent you the message again AND the person who they claim found the green bird one more time, flag it important and make the message subject something interesting that will catch their attention. Perhaps the person who refered you to the finder has their number. Tell them you'd just like to know its not your bird, even if they already reunited the owners.