apple ID no longer exist; activation lock

Restored my wife's iphone 6 using itunes, in an attempt to solve a "no service" problem, only to find out that it had the activation lock/find my phone enabled. The apple ID that is requested for activation no longer exist as does the email that was used to set it up (tried reset password anyway, website says ID doesn't exist).. So I called support.

It was confirmed by apple support that the ID no longer exist yet they can't do anything without some proof of purchase. I don't have a receipt.

Went to the AT&T store where the phone was purchased over 3 years ago; naturally they can't find any record of sale.

So did I just brick the phone? I can't come up with any ideas to convince apple support to unlock the phone.

The whole apple ID thing is weird though. I can log in with our current ID, look at the device list and see that the iphone 6 in question is displayed as active, along with our other devices. Shouldn't that be some kind of proof of ownership? I'm thinking there is some glitch in the system.

I did find out that the obsolete ID was set up my wife's father years ago and the "find my iphone" was activated on that account, then at some point he made a new apple ID for his devices. Of course he doesn't remember the password but it doesn't matter anyway as the appleid website indicates the account doesn't exist..