2002 Expedition Transmission

After dropping my trans pan today I found a yellow, plastic object with a o-ring on the round end. The other end has a post coming off of it (resembles a kids top). I can not locate where the o-ring end or perhaps the the post end inserts into the transmission, any help would be appreciated.

Brian

That is from the factory,sealed up the dipstick hole when it was built.Discard it and there is nothing wrong with your transmission without it