I have had this issue just now. Gremlins, I suppose.

Luckily though, I was going to respond to someone and I had received an automated GW email saying that someone had replied to my post and the email contained a link to the post. Since I could not find the post by looking or by using searches, I went to the automated email and clicked on the link. It took me to the post, where I entered a reply.

However, although I can see the post on the forum now (Computer Help Forum), my reply does not appear when I went back to the post. Still not there but, like I said, I can see the post listed now.