As I said, user with 10k+ can see deleted post if you provide them with a link to the post. So if somebody provided links to this users posts, any 10k+ user could see it.
@Bellatrix If you give me the link to your question, then I can view it. (And so can you if you still get it.)
Or if I find the link in some other way. But there is no easy way to find deleted posts.
Possibly in this case - since it was deleted recently - then they could be visible in 10k tools. Or with some additional information it would be possible to find it using SEDE - after the next update.
@MartinSleziak Moderators can undelete comments which were deleted by themselves. They can't undelete a comment deleted by the user. See here. (Not a very good reference, but it has that information there.)