i'd say 50/50 chance the account was hacked before he sold me it, it's my fault for not getting a signed message. Not sure what indications that it was sold you looked for but you're the detective here. Here's the guy that sold me it:
Can you prove ownership by a signed message from an address, because that's what a handful of users are going to ask you 
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.Yes I can sign from an old address.
If you can provide such signed message within 24 hours then I will leave my ratings that I have left the account (assuming you are unable to get the account back), otherwise the ratings indicating the account has been hacked will be removed.