Loaned my Ram 1500 to a relative the other day and upon return the insert from the hitch was in the bed but the pin was missing. I had a pin with a hole that a clip key slid into. I was pretty sure ...
Not that I would ever recommend going without the retaining clip, reality is the pin is very unlikely to come out even without the retaining clip. The clip should never be under any significant stress.
I've had both and never had one come off. If it was an issue, you could expect there to have been lawsuits and an unsuitable design would have long ago left the market.