Was driving last night and went over someone's muffler which fell off someone's car and after that heard rattling under my car! Must have damaged something! So I went this morning to a mechanic and after having put it on the lift twice and as well took it for a test drive to see what's causing a rattling like noise, sounds like a piece of metal shaking! Or bumping under the car but they could not figure it out! They tried shaking every part underneath and could not figure it out! Anyone one with similar experience or have knowledge what it could be? .