I found it!

The one thing that Metro seems to do well!

If you lose your keys on a train or bus they’ll probably end up here. Judging by the massive amount of keys that they have on hand and that’s just from the last month.
Just wait five days and then make the trek to the lost and found office, “conveniently” located across the street from the Prince George’s plaza metro stop near the end of the green line.  They don’t even accept reports of lost keys since they find so many, so you just have to hope that they’ll be there.

I’m really trying not to complain about this.  After all I did find my keys!