recovering a phone

If the previous owner was a family member, contact Apple. 

How to request access to a deceased family member's Apple accounts - Apple Support.    *

Apple ID - Official Apple Support.   -

Contact Apple for help with Apple ID account security - Apple Support.  *  (Link doesn’t always load)   

Get Support    -  Work through the screens to get a chat option. 

Apple Support schedule phone call.  -

https://twitter.com/AppleSupport   -  

It won't be deleted unless Find My Phone has been turned off prior to restoring the phone.

Only workaround is to have a proof of purchase.

My bad, I think I’ve even mentioned this once in a previous answer to another post, but I totally forgot about that. I can’t edit my answer to fix it, so just please ignore it OP.