The E90 M3 does not use an upper control arm.
Knowing that the car was damaged on the right side (passenger side) provides a few more possibilities for the excess negative camber. Here is a simple list:
1. The strut tower was damaged and not repaired. Possibly pushed in during the accident. A good body shop can measure the upper strut tower to confirm that the unibody is correct.
2. The suspension strut is bent. The alignment SAI or KPI readings will confirm damage.
3. The right wheel rim has excess run-out that was not properly compensated during the alignment measurement. You would likely have noticed a vibration or shake in the steering wheel.
4. The swivel bearing (lower part of the strut assembly) is bent.
5. There is always the chance that the alignment readings are incorrect as provided because of mistakes by the alignment technician.