What have you lost under the hood?

[400E]

I changed out my thermostat (2nd replacement, 161k miles) today. In the process of removing the hidden bolt in the back, I dropped a deep 10mm socket and can't for the life of me find it. I probed around with a magnetic retriever, checked on the ground, and took off the lower engine sound encapsulation panel, but never found the darn thing.

Rest of the job went OK. I stuffed some paper towels in the nooks and crannies so that if I dropped a bolt, it wouldn't wind up lost, too.

Right now, I've got my fingers crossed that the socket is safely tucked somewhere under the water pump and won't come out and into the pulleys!

Just wondering -- is it just me, or have others dropped things into the black hole, never to be seen again?