I'm curious how many smaller planes have gone missing that had less than a max of 14 passengers.

In the winter of 1996 in northern New Hampshire, a Learjet 35 (8 passengers max, but only carrying the crew) went off course in a storm on Christmas Eve and "disappeared". I was a cub scout at the time and our troop was one of the many search parties. We spent a couple days hiking and searching around Smarts Mountain in northern New Hampshire but were unsuccessful. The wreckage wasn't found for almost three years and ended up being quite close to our search area in a dense forest alongside the mountain. Afterwards, a law was passed requiring all US-registered business jets to carry distress beacons.