So, the reality of the camping thing is that he accepted an invite to a buddy's cabin. That's a whole lot less work than planning a camping trip with your S--especially if there is strain in the R and pressure to make it "memorable."
FWIW, I do think that he expects you to pursue him. It gives him the secure feeling that if he stops running, you will be there--for a booty call or just in general.
Have you ever tried to play frisbee with a dog that wants to play tag? If you refuse to chase him, eventually they will come back. Then they'll try to play tug-of-war with the frisbee. Finally they will drop the thing and wait for you to play YOUR way.
So, with the wedding, you are reasonably sure that he saw it on your calendar. (He was also maybe looking to see what was on for last night.) He wants you to ask him, but only because he wants the pursuit so he can run away some more. So don't ask him.
On the off chance that he really has forgotten, it's because it's an "appointment" and not a "party" in his head--guys may be bad at remembering appts, but it's because they don't want to go.
