maybe put a camera in your car that records while parked. if it happens near your home..chances are they live near you.
I dont think a clear bra would help, they will probably cut through it.
hire a ninja to keep watch
2013 F30 335i M Sport AW, HK Sound, Black Interior. 6 MT, M Performance Knob, 15% tint all around. OPTI COAT, M Performance Exhaust
Will be adding the PPK (if they ever make it)