Apple declined to remove Activation Lock

I have proof of purchase of an iPhone 14 that I let a girlfriend use until she lost it after not paying her share of the service for many months (service had been in my name the entire time).

I sensed that she lost it because she wasn’t responding to my texts/calls. It shows in my FindMy app, so I put it into lost mode with my phone number as the contact.

Then I got a call from a service that buys used phones. Someone was trying to sell the phone to them. They intercepted the phone and sent it to me after I provided them with the full description, including IMEI , the serial number, and also my affidavit stating that I am the owner of the phone.

When we set the phone up, I allowed my girlfriend to use her Apple ID, of course. Otherwise, why would I have her use mine and know my password, etc.? I have two other iphones in use under my apple ID - they are linked together for sharing the same Apple ID. So, using my ID for a phone that my girlfriend was using wouldn’t make sense.

So, as of now, this same girl is not in contact with me any longer. She’s unemployed, homeless the last time I saw her - the phone was still lost at that time - she gave me a phone number to reach her, but it may have been the wrong number or she lost that phone, too

I obtained the proof of purchase, sent it to Apple Support with my request to remove the activation lock, but they declined to do so without explanation or personal accountability, which is just wrong and very upsetting.

These phones aren’t exactly cheap, and my time is valuable. I’ve had to jump through several hoops at my end, and apple support appears to be smug about it: to investigation, no conversation. The phone has been erased already. It’s just the activation lock that’s supposed to protect me that is actually having the opposite effect. It’s created a loss instead.

What am I missing? What’s my recourse?

[Edited by Moderator]