Hey Jake - It is the same piece as this.
Several years ago forum member trimer posted a picture exact to what you found and what I found. All 3 of us found the piece in the drivers side footwell of 2001 or 2002 S cars. At the time no one could identify the piece. Maybe this time we'll get lucky.
Whatever it is, in the two years since I found it, the IMSB has not gone south and neither has the rear main seal or the water pump, so I guess we'll be ok.
edit: BTW - I think it's clutch pedal related. Mine dropped on my foot the same time I depressed the clutch pedal.