You have to add the snaps to the curtain. Walmart carries snap kits. Male part goes on the wall with pop rivets, female part goes on the curtain. It sounds like you have the male part of the snap still on the wall so you will be putting the female part on the curtain.
While you are at it, you might put a 1" X 2" thin plastic piece as a reinforcement for the snap on the curtain. Make a fold in the curtain, slide the plastic into the fold, drill through for the snap post, then mount the snap. I haven't tried this yet, but the curtain is prone to tear at the snap when you unsnap the curtain from the wall.
1978 Argosy 6 Metre Minuet
2006 Toyota Tacoma