I recently replaced the entire stock stereo in my '93 300E and came across this mystery plug. There's a plastic panel underneath the dash on the passenger side (underneath the airbag); when I removed it this dropped down. Because there's so much stuff under the dash and because my hand's too big I couldn't figure out where the other end went.

Any idea where this is supposed to go? And is it being unplugged a bad thing?

Thanks,
Mike