Sounds like a glitch. Send a ticket.
Mopup - The mop up setting is used to designate a pitcher to be used in blowouts (either winning or losing). Blowout is determined by the deficit (or lead) and the inning, e.g. an 8 run deficit in the 2nd inning would not be considered a blowout, but the same deficit in the 8th inning would be. Mop up designated pitchers could possibly be used in non-mop up situations. They will always be used before pitchers marked as 'rest'. For example, if you have 5 relievers and 1 is marked as rest, 1 is marked as mop up, 1 is marked as long relief, 1 is marked as setup and the last as your closer, and your game went to extra innings, if your closer, setup, and long relief had already been used, then your mop up pitcher would see action.