It may not have been a hangfire in the sense that most explained it. It could have been the striker, hammer, or whatever was delayed in acting. Ifteh trigger "clicks" the sear engagement but the hammer hangs up for whatever reason it could drop after the gun is on the bench.
As mentioed before, always lock or block the slide back or cylinder open when you lay a handgun down at the range. Empty brass can be used for this in a pinch, but chamber flags are cheap and easily seen to verify the action is open.
