I had someone do that to me because they had some issues with my fictional content. They never communicated and later slandered me ^^; along with doing other illegal and questionable things.

I've never heard of someone getting banned over that thankfully, the ownership log acts as proof of who made designs and it's never your fault if someone chooses to remove their own credits from art/ designs on here.

I believe some people do it, so they don't feel associated to a user they don't like. Some people even get harassed on here as a result of leaving credits up to someone who their social group doesn't like and are pressured into removing them.

I'm sorry it happened to you :(  Luckily there's little chance of you actually getting banned over this. 

whats funny is that this does nothing because like. you can check the ownership history to see who has been given credit in the past anyway

there was an artist who did this to me and other people who owned their designs. im still not sure why, but they were a really insecure person who usually moved accounts often without telling anyone. i usually tried to just credit them using the offsite artist option, then link their toyhouse as the offsite credit. usually designers/artists can remove their credit, but if its offsite i dont think they can

ive never heard of someone getting banned for this though. it could happen because of the rules i suppose, but just try to do the thing i mentioned above if you can! if you need to find credits again, you can look back at ownership logs / transfer logs in settings

Manually link to their TH rather than using the 'on-site artist' credit if you're worried; I don't think anyone can remove that.

I have some characters/art by an ex & I don't want to make them uncomfortable by directly crediting them & having my name show up in their inbox so I just use the Off-Site credit option with the URL to their TH since they don't use any other art sites. Not sure if this helps but hopefully it'll at least keep you out of trouble. ^^

Edit: Saw someone else suggested this already, good!

I'll be honest, I attempted to detach my own name from some designs, and the artists' names from characters/ designs that I've had really nasty blood attached to but I still want to keep the designs. They're still credited as the original designer (I can't fix that without deleting the character and reuploading, and trust me I've been fucking tempted...) but the "art" attached/ credits for the art are gone. 

I've adjusted their profiles to be completely hidden while I cope, too. 

It's sadly 100% intentional, I don't think it may be entirely malicious, depending,  but it's done manually. 

You won't be punished for art credits being missing. Only if you remove them yourself and change them when th adds them back IF that happens.

You can see the previous credit link if it was on site in the ownership history

I don't think I've ever run into this problem 

However, I have had people specifically say they don't want their TH directly credited because it will clog up their designs/art tabs. In those cases, they  usually say to credit their TH by using the off-site artist option and linking to their TH that way

I'd say that option could work here as well. You give proper credit and they can't remove the credit maliciously

if you remember the artist you can add the HTTP link in the “offsite artist” credit box and itll still link back to them. that way you dont have uncredited art/designs thatll dink ur account. 🤷

thats how i do bases unless told otherwise. 

Have you tried reaching out to the creators? I prefer to not attribute malice automatically, and it could be a mistake.
Barring that, I guess you could recredit them as the creator as an 'off-site' creator, but using their ToyHouse if that's a thing you're worried about. I haven't encountered that (or noticed it if it's happened, more specifically) but that at least will make sure the design is still credited.