Board Thread:Support Requests - Getting Technical/@comment-2020924-20150531065600/@comment-24409505-20150601084810

Once I also saw a page with a semicolon (let's say it was called ":Test") listed in the Special pages, but when I click it, the page doesn't exist. It was always there, even when the cache for the Special pages was refreshed. Then later I enabled the Top 10 List lab feature and I noticed the page was now called "Top 10 List:Test". I could then visit the history of the page and remove it.

I don't know if your situation is the same, but it could be that ":Layout_1-2085" was created in similar circumstances. Try enabling all wiki features and check if the page name changed?