OMG - my sides are hurting from laughing (not at you - the other guy)! That umbrella shaped thing is the plug for that mounting bracket you described, but that guy's plug obviously fell out and ended up sitting in the drain plug hole and he thought it was supposed to be there! Glad he's not my mechanic. Actually, it because of bozo's like this that I try and do as much of my own work as I can.
Here's your part number: 986 561 655 00, called an "interior cap"
They're cheap - order two! Please don't use them to plug your drain
Here's the page from the parts catalog that shows the part (it's #21)
Mark
Threaded Mode
