First you have to understand there are no warning lights related to mechanical damage. In particular, the Engine Computer monitors a lot of sensors and a lot of engine operating conditions. When it detects a problem it will store a diagnostic fault code, then it will turn on the Check Engine light only if that problem could adversely affect emissions. There's over 1000 potential fault codes and about half of them will not cause the light to turn on.

"the guy told me as long as nothing is leaking you're fine"

That is not the kind of reply I would expect from a professional, but I don't know what he found, if anything. Something could be shifted and rubbing on a radiator hose, and it WILL start to leak later. I'd hardly call that "fine". You are right to want to at least identify the cause so you can determine if it will cause trouble later. A lot of plastic shields and liners are held on with plastic rivets. Those rivets will break and relieve stress before those parts will break. All body shops have new rivets. Those shields can vibrate in the wind or from normal engine vibration. If you can't find anything loose or broken, visit a body shop. Those guys are real good at finding hidden damage, and at putting things back the way they are supposed to be.