With all due respect, here we do NOT go again.
Looking at the admin logs, doesn't look like anyone has made any changes. There is (and always has been) a limit on how long you can edit a post. After a certain time, you can not edit a post. Seeing as your last post (prior to the one I'm replying to) was 11 hours ago, this would be beyond the amount of time that editing a post would be allowed.
How long of a time are you allowed to edit a post? Well, long enough to correct typos, or other information you figure out shortly after posting. However, not long enough that one could change the content of their post in an attempt to make others look bad. (Yes, it's happened.)