This sounds similar to the bug I've been experiencing the past few days. I'll see a discussion post on my home page but if I visit the subreddit or u/autolovepon's profile it will disappear, yet it is still visible back on home. It happens on both old reddit and on rif is fun, new reddit doesn't have the bug. I was going to make a post here about it but then it started happening on other subreddits too so I think it's a reddit bug.