OK........... The old wives tale about locking up an engine by doing this is un true but..... Your car still won't run with it in the gas tank. You need to have the gas tank drained (preferably) dropped and washed out. Fuel filter needs to be changed and if fuel injected the injectors cleaned by running a heavy detergent cleaner through them which most automotive repair facilities have on hand. Check with your insurance company you might be able to claim this under vandalism but not sure. FYI.