Fortunately, the posts of users whose accounts have been deleted remain available to view. However, I can no longer search for them. A search for "user:4032" yields nothing.
Is this a bug? Is there an alternative way to search?
It exists. You need to use SQL? for database of this site.
select
id as [Post Link]
,body
,owneruserid
,ownerdisplayname
from posts
where ownerdisplayname = 'user4032'
Click Run query in the link below. ("japanese" should be a placeholder for this site. You may change it to any site you want to search)
https://data.stackexchange.com/japanese/query/edit/1552853
cf.
How can I search for posts by Deleted Users?
(This question seems to have been asked over a decade ago, but it has been Viewed only "289 times" on Meta Stack exchange...)