You'll see if a post becomes community wiki - it'll say so in the normal way.
If you're not getting rep for it, have you perhaps hit the daily cap without realising it? There are some times where it doesn't look like you've hit the cap, but the internal counter (or whatever) thinks you've hit it. This is particularly true if any posts which have scored you points during the day have been deleted. (For example, I'm currently on 225 for the day on SO despite having 3 accepted answers after hitting the rep cap - the effective rep cap is 180 for me today.)
If you go to the reputation part of the recent activity tab (via the envelope icon, not your user profile) what does that show for the post in question? It should show the number of votes received and the reputation gained.