i can't say for certain, but i think it's just waiting for approval. posts that are waiting tend to be hard to find, and sometimes look like they disappear altogether. back when i first joined, i had a few posts that went through that process, but they turned out fine in the end. i'm sure it's...
i think it just has something to do with how the website or server runs; i've been on a lot of forums, and they all seem to count views and online status the same way. forums tend to be really similar with how they run, so i'm guessing it's a pretty universal thing.
edit; don't take my word...
it keeps showing you and everyone else who has clicked on the thread as viewing for awhile. i believe it goes away after an hour, but i'm not sure if that's the exact time limit.