Thats really out of order, if theres one thing that pisses me off its vandalism of other peoples property/belongings/especially cars.
I've had stuff along the lines of this happen to myself, i've had people come to my house with the intention to do things to my car and when it wasn't there they decided to do it to the house instead.
Might be worth looking around the area to see if any chav's have written their name on walls or bus stops in gold paint? At least theres the chance of the cctv
getting them but its still no conselation for whats been done