[Dangerous Doug]

Before digging around in your transmission, I'd look with a flashlight into the cable hole to verify that the gear COULD fall off, into the transmission. It's hard for me to envision an engineer that would design the transmission in a way that the speedo gear could fall off and drop into the pan.

I'm thinking the gear came off with the cable and then fell off when you weren't looking.

At least, that's what would happen to me...

...and I'd probably find it after I pulled the pan on the transmission...

DD