Facebook will literally dump account info to law enforcement... all message history, account activity, etc.. it would show the cops whether this is a standard MO of the scammer, something they do a lot, possibly implicate them for drugs, theft, whatever. It doesn't matter if they deleted from their messages or account... FB still has it. Along with any other personal info they provided... email addresses, home addresses, schools attended, phone numbers, legal names, contact lists, check-ins at different places around town, etc. And any photos they've uploaded, like other items that are potentially stolen, including the phone OP purchased. Which would back up OPs story of having purchased a phone that 2as previously stolen, and they didn't steal it themselves.