Cant comment on the TT but most VAG cars have a switch in the glovebox that is activated by the key to disable. When disabled a light on the dash lights up to remind you it's disabled
Most of them have a door type lock in the glove box, on the right in the A4, it is easy to spot if it is there.
Put main key in and turn to off and you will get warning somewhere in the car, could be on the dash, on the A4 it is on the ceiling next to the light controls...
