I have seen two license plates that apparently fell off cars and were retrieved and are displayed. They both appear to be front plates because they do not have tabs for year or month.
One is in the parking lot of the Bank of America at 13th and East Madison (A__6599).
The other is leaning against the curb on the west side of the 1500 block of 24th Avenue (A__0355).
I am not showing the full license plate numbers because I think it may not be appropriate to do so, for privacy reasons or whatever, but if yours is missing and includes the characters I have given, it’s probably worth checking out.