You were changing transmission filter and a plastic bulb with an o ring on it came out of some where dont know where it goes?

This drove me nut's, the only place it looked to fit in was in the filter where it goes into the pump, I wonder if anybody has put it there, well don't. I keep mine on the workbench as a reminder to Google stuff before getting frustrated.

THROW IT AWAY is the answer, It was to plug the Tranny Dip Stick whole during vehicle assembly. The plug was pushed in when the dipstick was installed.

Also lets you know the tranny is having its first filter change.