I think some parakeets escape at pet shops.

The big Meijer's near us has several flying around the store and cheeping.
They have been there loose for weeks now.

They seem to hover in the rafters near the entry door. Sparrows also
get IN the store as well, since they nest near the entry.

The big stores tend to have uneducated help(pet handling education), and I think the birds escape
these employees easily.

If you have time.... you can try to hand train him. This technique is used for outdoor birds, like chickadees.
You have to sit in one spot, and not move and let him get used to you. Then you put food near you on a table
or whatever, and don't flinch when he comes to it. Then you put some in your hand or on your knee, and sit
very still and the bird will eventually come to you. I have only done this with chickadees...but if this parakeet
has been a pet he may train to you more quickly. But you have to be there for a while to earn the trust.