Would it be inappropriate to mention that I found a ring?

My fiance is going to be leaving for the Navy at the end of October. We informally decided to get married sometime (probably within a year) and therefore informally decided that we're engaged now. So there was no ring or actual proposal - he said he would "propose" to me later on when he had a ring.

Anyway, we were in his room and I went to look for chapstick. He keeps it on one of the shelves in his closet. Sometimes it gets pushed under a stack of shirts, so I lifted up his shirts and I found a really pretty engagement ring/wedding band set (it wasn't in a box). I didn't say anything to him. I'm really happy and excited, but at the same time I feel like a kid who found their Christmas presents! I want to wear the ring now, but I don't want to ruin any plans he had.

Should I say something to him? Or should I just pretend I didn't accidentally find it and then wait for him to give it to me?