http://pittsburgh.pirates.mlb.com/pit/ballpark/pit_ballpark_guide.jsp
BIKE PARKING/RACKS
Bike racks are located outside the ballpark on Federal Street near the Roberto Clemente Bridge entrance to the park and at the southwest entrance near the Allegheny River. Bikes are not permitted inside the ballpark.
I don't see anywhere in that statement that permits them to remove your bike? Did you park in the ballpark?
// FYI I sent an email to the Pirates inquiring about the policy which would permit them to do such an act.
Was there a "no parking" sign on the meter? They may have considered the full scope of the law. Whereby, any vehicle parked along general robinson, federal, etc would be towed or removed: car, truck, motorcycle, pedalcycle.