The speed sensor stopped working?

Transaxle-mounted electronic Speed Sensor. The speed sensor stopped working months ago, and I have since replaced it AND the ECM. It's still not working. As a test, I attached the VSS harness to the old sensor, and rotated it with a drill. The speedometer worked, so I know it's not the VSS itself or its related electronics. As I probe the VSS port with a finger, I find no gear to spin the sensor, at least that I can recognize. I feel one gear that has severely slanted teeth off to the side of the port, but it would spin in a direction along the length of the shaft. It seems that there should be a gear between it and the VSS shaft. Here's the curious thing, a week or so ago (before replacing the VSS and ECM) the speedometer briefly kicked in. Is it possible that I dislodged a gear from its seat while removing the old VSS, and it fell into the transaxle housing?