I think this might be a general problem with the mouse, as my Mac will show "Connection lost" with a mouse icon quite a bit when the device goes idle. Lucially, OS X seeks out bluetooth mice and keyboards quite activly, and refinds the mouse quickly if I move it around.

It's still being returned though soon, just too many problems with it for me to deal with. I'll wait it out for the Logitech one due out soon.