I believe highly you only need a HP to be with you when you see
suspicious characters loitering around the carpark and starts to
show it on your boyfriend bike. Use your HP dial 999 or check the
nearest NPC before your deployment. As long as you are the key
witness and damages are done on the bike. I doubt he has the chance
to deny.
Similarly, I do believe the vandal has something to do against with
your boyfriend certain actions. Could be offended somebody elses.
Or, you ask your boyfriend what he had done on road to other
motorists. Else, could be an asshole playing punks liao.