Can anyone shed any light on the following?

Went through Warkworth on 7527 at approx 17:40, then pulled up behind 7481, with it's hazards on, screened for the X18. No passengers, our driver went and talked to the one on 7481, came back and we drove off.

Was it allocated and broke down? Was it sent by mistake? Seems very strange, especially as when we were leaving Amble we passed it, all lights off, no destination on, making it look like it definitely hadn't broke down?