I’ve had this happen a couple times.
I am writing a decenly lengthy post to an existing thread. After I hit submit, my post is the top post on the second page, so my post is the only thing I see.
For a second I think, “CRAP! Did I just screw up and make a new thread?!” I feel like an idiot for a second, and then “Whew…”
Please tell me I am not the only one this stupid.