Actually, I think your chances of being taped or watched are greater at an MP rather than a private 'incall' massage. Generally the term 'incall' is used to refer to an SP rather than an MPA operating out of her home.
You can make a general scan of the room to look for recording or video equipment. However, the best protection against future problems would be to leave as little identifying info as possible with an unknown MPA and always pay cash, never credit card or cheque (as Jerry Springer has come to regret).