Any help of advise with the following would be appreciated:

I have Golf GTE Advance Mk7.5 that I have had from new since August 2017 that has now done 8284 miles.

In the middle of November the car was stolen off my drive and was joy ridden for approximately 10 miles resulting in various damage.

The main damage was a cracked rear disc on the driver side that was replaced. (only this disc was replaced)

I got my car back repaired at the beginning of December and all was fine.

However since about the middle of January I have noticed an increased vibration and shuddering on braking.
This has gradually got worse and worse from January till now.

Yesterday the car went into the garage for the 1st service and they have advised me that the all the brake discs are worped.

My driving style is pretty standard and have never had this happen in my 28 years of driving.

Could this be in anyway related to when my car was stolen?
Is it a possibility that any damage caused by the joy rider could take a while to get worse?
Should the crash repair garage have replaced both discs? Could this be a cause?

I use the adaptive cruise control quite regular, could this be related?