@Mr @ Spotty M, yup, i'm sure. Was shuttling between txl and cgn that day myself (usual four sector short haul day) and did spot a monarch plane in txl later on myself, however couldn't see the registration as it was somewhat dark and i had to make sure nothing happens to my plane
In CGN it was parked around D20 on apron D opposite to terminal 2, one stair attached, doors closed, no lights. In txl around position 62 at terminal C adjacent to taxiway PE.