An equally strange occurrence happened to me awhile back:
We were mostly boarded at DFW on a LUS 321 (this was around the time that the LUS crew and aircraft were separate from LAA but the LUS 321's were starting to creap on DFW routes) . This was a RON plane and apparently there is some sort of security sweep that's supposed to happen first thing in the morning for these aircraft. The pilot announced that this security sweep did not happen so everyone had to deboard in order for this task to be completed.... then we re-boarded.
The FA's were quite vocal that they couldn't believe this oversight could happen at DFW "isn't this our new headquarters?" quipped one of them
Whoops