We often merge duplicate threads, and/or move threads to more fitting sections. Sometimes we will delete some duplicate posts during a thread merge, which would cause your post count to drop (and also cause the duplicate thread to disappear). If we move a thread from a section where posts count to a section where posts don't count, then this would also cause your total post count to drop. Some threads get removed from the public sections if they violate site or section policies.
If you have posted a thread that may have been moved to a different section, you can always find it by doing a search under your username, or by clicking "My Recent Topics" in the header tool bar.
For detailed info on site rules, sections where posts count/don't count, etc., see this link:
https://ls1tech.com/forums/user-supp...questions.html