I never seen anything like that. Assume what happened is a software glitch in the cluster.
The DCF77 protocol is error tolerant due to presence of parity bits P1, P2 and P3 in the signal.
The following validation methods are applied:
* parity bit checks: whether the received P1, P2, P3 parity bits are the same that were computed from the received data
* range check of received data e.g. whether the received 'Month' value is smaller than 13, etc.
If signal is received with an error another attempt is made. Information about number of synch attempts and and when the attempts are made is documented in this thread. If all attempts fail for a certain period of time the mast symbol will disappear and the clock will switch to manual mode until first successful synch.
I confirm that the mast symbol in my car never ever disappeared after I installed the receiver in the OEM location.