This deleted question still appears in the search results if you look for its content, e.g. when searching for "it seems they forgot to take the square root in the denominator":
SEDE says it has been deleted on April 4th, so it can't really be a caching issue.
Note for ♦ moderators: I have a hunch that undeleting and redeleting might solve the issue; perhaps it's better for the developers' analysis to leave it like this. They do monitor bugs on child metas.