Just a clarification - you cannot make "your own" wiki on Fandom. You can found a new wiki about a topic if there is no wiki about it yet, and you become the admin of it, but it's for everyone interested.
If you can't find it on Special:UserActivity, you could try looking through Special:NewWikis or searching for it using Special:SearchCommunity. General web search engines like Google probably won't have found the wiki yet but you can always give it a try. If you really can't find it, then it is possible it may have been closed.