Interesting. Is there someplace cases like these are recorded?

Sort of. This is a list of the subs that don't show up on s/all (our shadowbanning)

https://saidit.net/subs/notall/

Now some of these subs are self-quarantined because they are meant to be private. Others such as s/incels had a moderator that refused to follow the site rules (they banned people for non-rule violations) and so were removed from all. Magnora also would put subs he didn't like on this list without notifying anyone.

debatealtright is visible now, he must have un-shadow-banned it at some point later? what happened?

Yeah, it started showing up again maybe two months ago, after many months of being being removed from s/all. I'd be surprised if it was magnora that unhid them, as he hasn't been around when it came back up. I am not one of the regulars in that sub, so I don't know the details. send_nasty_stuff (the sub admin) or one of the regulars there would be able to tell you more about it. Or maybe Zapped, as he is the most active of the current site admins