I guess curiosity and OCD have kept me out of this situation for the last 35 years. I always look at the face of the filter when I take it off, just to see if anything looks peculiar. A missing gasket would definitely sound an alarm. I always clean the filter housing of all old oil. In 35 years, I've had one Fram gasket stick to it. I'm very surprised how many people I've seen on the internet that have made this mistake. My own brother, who worked as a mechanic on a funny car team years ago, made this mistake about 5 years ago. I can't even imagine just spinning an old filter off, and screwing a new one on without looking and cleaning first.