Oh, some guy wanted a solution to a (homework?) problem. It wasn't the particular thread that was an issue for me; I just thought it's disappearance was odd.
Ah... I'm guessing it was because the OP was reported. I just remembered that ;)
There are some issues with this that seem a bit odd. I think the deletion and reporting should be separate.
I have reported spam posts that, due to the new user status of the OP, have been deleted straight away. This is a good thing.
However I have also reported a thread for being in the wrong forum (requested it be moved) and due to new user status of the OP, the top post was deleted. This is a bad thing.
I also believe that there should be more openness in the reporting process, showing who reported it and why. Also I believe it would be informative to have a 'place holder' that states why something was deleted, even if this is removed after some days.
When the first post of a thread is deleted, the whole thread should be deleted, if you ask me. Archiving a bunch of useless drivel only hurts the search feature when you actually need to find something.
Unfortunately, for the common user, I find the new changes (just the report/delete ones) more frustrating than the old report and let the admin clean it up later. I don't see any less spam now than before but there seems to be an over-abundance of threads with missing posts and repeated discussions about how it either doesn't make sense or why people do that.
I find myself checking the forums less frequently than before and posting far less. There seems to be about 1/10 of the interesting discussions that there used to be a few years ago. Easily 1/2 of the regular posters are either lurking or otherwise MIA.
I have seen similar trends on other forums: more junk threads by the day and far less information. It could be coincidence or perhaps online forums are in decline (vs. LinkedIn discussions, facebook groups, and other "newer" outlets).