Hi @EmjaeD,
The "undelete" trick can definitely help with some tricky situations like this, but as you've found out here, there are a limited number of things you'll find on that page and no way to get load more or anything. As I understand it, the undelete page was built for Canvas support to utilize many years ago, and isn't really an officially supported feature. Word has obviously gotten out about the undelete page through the community, and if what you want is listed it usually works decently well. The only "easy" way I know of to get additional things listed is to start restoring things you don't actually want, then reload the page and it'll list some more. That's a very clunky workaround and could potentially make your course worse depending on what you restore.
I would advise you to contact Canvas support if your school/institution gives you access to them. They may have some other tools to restore content, but there is really no guarantee of that.
Hope this helps, sorry there isn't really a better solution to this.
-Chris