Anyone familiar with what the hell this is?

I had a busted center carrier driveshaft bearing and removed the piece of shaft from the transfer case to the other piece of shaft that comes off the rear axle. I removed the two bolts on the carrier bracket and the 4 bolts from the end of the driveshaft. When I slid out from under the truck, this piece was on the driveway where I was...I dont see where it would have from. I found this before I even removed the bearing from the shaft. I didnt touch anything else. HELP would be appreciated.