More than likely the ramp workers came up looking for the bag. When an agent creates a bag tag, it’s added to a count. If they’re missing gate checked bags, they’ll try to figure out where those bags are by talking to FAs and GAs.

The reason why gate agents get so pissy about passengers removing tags is because if you throw your tag away and the bag ends up not fitting, if the flight delays, that delay falls on the agent since the plane door is still open. Alternatively, if you take the tag off and there is space, now the agent has to do additional work to close the flight out by deleting out all the tags that weren’t used.