What is this part for?

I found this spring, about 1 inch long, under my car after some weekend work.




I changed the manual transmission fluid on my '04 TL. I removed the lower engine cover to access the drain area, and also removed the battery compartment and opened the air cleaner in order to get easier access to the tranny fill plug.

Anyone know if this belongs to my TL, or maybe it's just some random part from my kids' toys that ended up under the car?

Thanks in advance for any help you can provide.