What is this mystery part?
 

Knocked the band off my air hose yesterday when reinstalling. When I got my claw out to fish it out, I noticed this piece was laying down there with the band. It was lying there loose and I could not tell if it was something that came loose when I jarred the air hose. It is soft rubber that seems like it is breaking down. I recently replaced all the solenoids behind the UIM so there was a good bit of disassembly going on. Anybody know what it is?

Here is another picture.

Looks like the bleeder screw cap off the clutch slave?