By all appearances, this is just a scam, so beware.

AFAIK, they sell you a ticket via PayPal, and they buy it from an OTA with a stolen credit card. It's called the "triangulation scam" and when the airline or OTA figures it out, potentially months later, it's too late for PayPal's protection.

Important note here is that although you could be past PayPal's window, if you paid via PayPal via your credit card, they likely have a much longer window. Pursue from that angle.