I did that, but in high school. I was the class clown though, so luckily everyone thought I was just being funny. (A lot of things I said quite seriously were taken as ironic.)
I think he remembers it but holds off saying anything until he knows Phoebe went back. Maybe after the conversation about how he liked camp, he’s already suspecting this is the, well, time.
I love the way Gladys is following the conversation.