I dont leave notes in my car. Fortunately in the highlands break ins like these are very rare. I've parked at Achlean many times and the only thing that concerned me are the no overnight parking signs. Unfortunately nowadays the highlands are joining in the car park profiteering game and the people most likely to rob you are the folk running the car park.
I didn't hear anything about the Achlean car park break ins and it doesn't even seem to have made the local news which is surprising for such an unusual event. Be good to hear what the full story is if any one knows, because the info in Camerons article is a bit vague regarding the actual break ins.
A good deterrent might be putting warning cctv camera stickers on your windows which may deter the opportunist thief. I haven't bothered doing this myself but have thought about it though nothing will prevent someone who is determined.
Biggest problem I have found regarding this sort of crime and vandalism in particular is that even on the rare occasion when someone is brought to justice the courts are far too lenient.