This question already has an answer here:
I'm on some (single) SX site, call it foo.stackexchange.com . There used to be a user named JoeUser, with number 1234. That user has left, deleting their account.
Their questions and answers don't disappear, but I do not seem to be able to search for them:
https://foo.stackexchange.com/search?q=user%3A1234 doesn't work.
Can I effect this search somehow?