Welcome to FT. This is a board for the exchange of information, so if you pose a question, you get the responses. Not really up to you to tell others what you do and do not want.

Anybody selling tickets over Craig's List is 99.9999% a fraud and it is close to that % that after you turn over your money, you will not be boarding your flight (or worse, you will board your flight make it to Europe and be denied boarding on the way back). The former just means that your trip is gone. The latter means that you are stuck and have to purchase one-way tickets home at walk-up prices (which will be 8-10x the price you paid on Craig's List).

To answer your specific question, you could get hauled off the aircraft at any time until it departs. Having a ticker or BP is meaningless. If fraud is uncovered, you won't be flying and you can dream up as many safeguards as you want and bump right into airline security which is in place to prevent fraud.

Air carriers monitor air tickets like hawks. Whether you know someone who works at a carrier or not, the issuance of a ticket for $500 which ought to cost $1,500, pops out of the system as a red flag.