Should I be concerned?
 

So it began with white smoke coming out of the exhaust. Then on the highway it died with a odd noise. So thinking that this was a valve or something really bad I decided to take out the motor. While following the steps and getting close to removing the mounting bolts I found the spark plug had come out of the mount. So I put the engine back in and now it does start but it is as if I don't have a muffler. It is loud. I took the pipes out and remounted them and it "seems" the sound is coming from the middle of the exhaust assembly. There are no holes but I can't figure where the sound is coming from? The concern of this post is the spark plug coming out? Thanks for your time!! Oh it's a 2009.

My first concern would be to check the threads in the spark plug hole. Either the plug was just loose or the threads have been stripped by some one with a strong arm and too much force. The condition of the threads will dictate your next move.

Regarding the plug issue, I mostly agree with WW2, but in my experience (yes, mine lol), if the threads are messed up/stripped, too much force could probably cause the plug threads to cut new threads and "feel" like it has been seated properly, and like a normally installed plug, shouldn't come loose.
The one thing I definitely agree on is if the threads are damaged and how bad, that issue will surely dictate your next move.

chandlerbingfl