There are new locking gas caps for Mavs on ebay all the time. With the price of gas these days it is prolly a good idea for protection from sugar vandals and siphoners alike.
I forgot something. I dont know if this would help in the future. I have double filters, one between the tank and the electric fuel pump and one a few inches before the carb. The one by the tank is the clear kind so you can see if any crap is in there.