In the early 1970s I flew for Valley Airlines, one of the early commuter carriers in California. We had 5 or 6 Volpar Beach 18s.
We were about halfway from Santa Barbara to Monterey, CA. For once, both P&W R-985s were humming smoothly. Suddenly, it got very breezy in the the cabin. I looked back (no cockpit door), and there's this guy gazing around the cabin with no emergency exit door next to him whistling as if to say, "It wasn't me!"
I slowed to around 90kts to lower the noise level, and we landed at Monterey.
The guy insisted that the door just flew off on it's own. No one saw him playing with the handle, so I couldn't press it any further.
The company flew a replacement exit door down from Oakland, and we continued the day's circuit. At San Jose, a woman remarked on boarding that we should paint our airplanes because that window didn't match the rest of the paint scheme
