What should i do with this iphone?

I bought a iphone for a $100 and i didn't kno until i got home that the phone was reported stolen. I contacted the original owner, the first time we talked i explained the situation and she said she will talk it over with her husband. The second time i contacted her she told me i would have to talk to her son about it because it was originally his phone, so i asked for her sons number she said she can't give it to me and i would have to contact her at another time. Now i have been trying to get into contact with this lady for weeks but she doesn't answer. She only answer if i call from a friends phone. I would return it back to her but she doesn't answer the phone, and i don't think she wants me to have the iphone. So what can i do with it being that i can't do anything with it without the oringinal apple I.D and the owner doesn't answer the phone anymore.

Added (1). the phone has been stolen for months so i'm sure they got a replacement by now. And i'm sure i didn't buy it from her son

The original owner replaced the stolen phone using their insurance. Are you sure you didn't buy it from her son?