In fact, you can see any of your posts provided you have a link. So basically the question is - is it possible to find link to my deleted question if I did not save the link somewhere?
There are two standard ways provided by MathOverflow/Stack Exchange interface.
1See the section "Can I see a list of my deleted posts?" in the FAQ post: How does deleting work? What can cause a post to be deleted, and what does that actually mean? What are the criteria for deletion?. And also some other related posts, such as: Show all of my question/answers to me even if they are deleted,Make your deleted questions and answers more discoverable, We should be able to find questions or answers that we have deleted, How do I view my old deleted questions?, etc.
2See also: Enable searching with deleted:1 for 10k users
If the above does not help you (i.e., the question is old and you are below 10k), you might still find the link in some other way if you are lucky.
EDIT: Now that any user can get a list of all their deleted questions (answers), this part is not really relevant if you are looking for your own deleted post. I'll still leave it here - in case some of the information given here might be useful in some other situations.
- You can try checking your browser history, if you remember some part of the title.
- Perhaps you can find question in some lists on this site. If you favorited the question, you can still see it in your favorites. If you received some badge for this particular question, you will find the question in the list of posts for which you earned the specific badge. (To display the list, just click on the badge in question.) If you deleted the question yourself, you can still find it in the list of your delete votes.
- Sometimes data explorer might help. The data are updated only once a week - it is possible that a question is deleted on the site but it is still in the database. Here is a query to find all questions from a specific user.
- You can also try Google Cache or Wayback Machine to see whether you can find there some version of your profile (or list of questions in a specific tag or some other reasonable page) which still contains the question you're interested in.
Moderators are able to search among deleted questions. (This is different from the possibility for 10k+ users mentioned above - they can only search for their own deleted posts.)
So if the above fails, you can probably ask a moderator for help. Past experience here on meta suggests that they were usually willing to help with requests to find some deleted questions. (And I assume they will also be willing to do this also in the future, unless such requests become too frequent.)
I will add that 10k+ users can see recent deletions - with the exception of self-deletions - in moderator tools. But this only shows the posts which were deleted recently - this is far from searching among all deleted posts as moderators can. Still, in some cases any 10k+ user could be able to find your deleted question for you in this way.