Been too busy to crawl under the dash with a flashlight and check it out. I wonder if that thing is why my SES light is always on. The light came back on the day after the dealership reset it, after installing the replacement CD player.
I doubt this thing came from the head unit, as I had taken everything apart and there's simply no opening large enough for that thing to fall out of. I only hope it didn't come from somewhere deep up in the dash, where I won't be able to easily access its home.
Eric...what is FSM?