Tank Mounting Problems of Toyota RAV4

As I was driving home (approx. 30 mile drive), I was hearing something that was thumping, thinking it was just my seat belt hanging out the door. I tried the passenger seat belt and it was tight, so I assumed it was just my seat belt hanging out the door. After arriving home, I noticed the seat belt was not hanging outside the door. I looked under the car to find a "l-shaped" bar hanging off the car. It was the bar that held the gas tank. I never expected something so important to a car would have let go. All along I am thinking is it still safe to drive the car to the mechanic because there must be a second bar holding the tank up. According to the mechanic, there is not. The mechanic told me I was a very lucky girl as the metal bar was the only bar holding the tank up. There should be a additional bars installed to give extra protection if one should fall off or become loose.