Deleted Reduce Interruptions focus & now I can’t get it back

I have an iPhone 13 mini with iOS 18.2.1. When the Reduce Interruptions focus was added to iOS 18, it appeared on my phone, to my surprise, and seemed to work fine. Today, I deleted it temporarily, thinking I could put it back, but now it doesn’t show up in the Add Focus page when I tap the + button. However, if I search for it by name in Settings, it shows up in the search results (tapping it takes me to Focus but nothing else happens), and if I create a new focus with the same name, I’m told I can’t because a focus with that name already exists. Rebooting did not help.

How do I get the Reduce Interruptions focus back?