strong gasoline odor when in enclosed garage

I had an older car once that had a rusty gas tank with leaking gas that would evaporate as fast as it leaked. Therefore, there were no wet spots on the floor but the tank was always wet with gas and you could smell it. You should have a different mechanic put it up on the hoist and look for wet spots. If you smell gas, there's a leak somewhere and that could lead to a fire in your vehicle and even your house. You're not dumb...the dealer is. Be safe.