Indigo Domotics

So I pulled out one of my *surplus* LampLinc modules to put it (back) into service, and noticed the sound of something rattling around inside. When I took it apart, I found a loose small cylinder (open on one end) about the size of a healthy pencil eraser. I have no idea where it belongs or how important it is that it be re-installed wherever it is that it goes.

Anybody familiary with this thing have some advice for me?

(That last photo is my guess at where it looks like it should go.)