Ok - I'm not saying I've had fabulous experiences with Dealers, but, your comments have to make me ask.
Why would they try to rip you off in that fashion?
It's one thing for them to refuse to do work, or fail to discover your problems; it's quite another to simply fail to give you the parts.
I'd ask - is there something about your experience that is prompting them to do this? Were you rude? Do you come across as somebody trying to get something for free? Is there any history with you fighting/arguing with them about something else? Or is this particular Service Manager that much of a weasel that they have to screw you out of $60?
In any case, regardless of whether your signature is on a piece of paper saying you paid, you do have recourse; particularly if you used a credit card and particularly if it's quite obvious that the hardware is not installed on your car. Consider talking to the dealership manager - over such a small amount of money as $60, I can't believe they'd even want to waste the time it takes to talk to you. They'd just pay it and get you out of there.
Lastly, consider complaining to the Better Business Bureau. Make the threat during your next talk with them, and if they don't help, FOLLOW THROUGH on the threat. Make sure they hear from others about your concerns.
Hmmm, about the bulb for the clock. I had zero problems buying a replacement bulb for the clock on a 95 MTX SE a couple years ago from a Dealership. For such a tiny item it was expensive ($5?).
Mike