Possibilities range from the totally innocent to the totally sinister.

On the innocent end of the spectrum ... some TSOs have reported here that they've gone to extraordinary lengths to return abandoned items to their owners. It could be as simple as a TSO doing a good deed for someone.

On the not-so-innocent end of the spectrum ... we've also seen situations where a passenger manages to escape exit a checkpoint without "completing screening", because the passenger innocently left the checkpoint without realizing that the screening wasn't finished. In those situations, if TSA could track down the passenger, I could certainly see them coming aboard the plane and insisting that the passenger disembark in order to be "properly rescreened".

Somewhere in-between ... we've had plenty of reports here of situations where gate agents get paranoid concerned about a particular passenger of color and ask TSA to give their opinion on whether or not the passenger is safe to fly. We've seen at least a few stories (recently, even) where TSA comes to a gate, interviews the passenger briefly, says "they're fine", and leaves.

So ... in the absence of any other information, there's no real way to know what was going on. But given TSA's propensity for dumping terminals, I'd guess that since you didn't experience a travel interruption, everything was probably just fine.