Missing exhaust nuts??

So I started having an exhaust rattle a few months ago. It slowly started to creep up louder and louder. Today is it pretty loud, so I assumed it was a leak that was slowly getting bigger. Well I finally had some time off and crawled under the truck and found that not one but two of the bolts on the flange are missing nuts.
Anybody else had that happen before? Usually it's the other way around from my experience. Impossible to get them off, not them falling off on their own. I'm hoping thats the source of the noise. Going to get some replacement nuts and try it out.

The flange that is missing the two nuts is right after the manifold, where the exhaust goes from two to one on a 2.7.

 

Also, anybody know what size those nuts are?

http://www.autozone.com/autozone/pa...filterByKeyWord=exhaust+nut&fromString=search

Found this little kit of two studs and two nuts, not sure if those are the size I need though.