I had something for this - A way to say you were about to drop a perfect punchline but

A way to say you were about to drop a perfect punchline but then forgot it like you forgot your pants on the floor

I had something for this, and now I’m just a guy who forgot his pants

I had something for this, but my brain was on vacation

I had something for this, and now I’m just a man who forgot his punchline