In short, if for some reason something big happens with forum where administrator is not enough experienced it can happen that Recycle bin hide most of deleted posts which will randomly appear later after physically deletion of visible posts/topics from Recycle bin. In my case there was only 2 visible pages in Recycle bin, 1st was with latest or with random post time of deleted posts/topics and 2nd page had oldest deleted topics, oldest date and time.
Why this happens? My opinion is after some shock that forum has suffered like some problem with broken sql table, or not properly installed/uninstalled mod/s, or after database was broken for some reason. Also very possible is Recycle bin to be too big to work so this happens or after forum is overloaded with logs which cause side effects and after fix problem is not completely fixed.
Admin can access to hidden posts/topics from Recycle bin only directly through User profile/posts (can't say if topics are separated and seen as recycled in ProfileInfo/Show Posts.../Topics). So whatever happens here result seems to be the same, only 2 pages available with recycled posts/topics and others usually appears as explained above.
Please read this topic, this member noticed exactly the same thing that I did about 2-4 years ago. I'm not admin anymore on that forum where I noticed it, but I understand completely what is happening to him now, not much relevant, I mean Recycle bin has purpose to delete topics, but its harder to find what is deleted because most likely topic/post will be hidden except if you know to whom post/topic belongs. Probably recently deleted post/topic can be tracked in logs, but I forgot about what happens there.
Thank you for posting this here, as I was going to also. If developers/admins need more information, I am willing to provide as needed.