If you remember some parts of the text of the question (title, usernames of user who participated there). You can try Google. If you are lucky, you can find that it is still in Google cache, or that one of the many sites that copy content from SE sites contains the question.
Basically the same holds for answer - if it was deleted recently enough, it might still be in Google cache. And some scraper site might have copied the answer.
Also if the deletion was recent enough the post might still be in the data contained in data explorer. But it might be tricky to find it there. See, for example, some suggestions given in this answer.
If you know the link to the question (for example from your browser history) you can get link to the cached version of the question in the way described here: How to modify a URL to get a Google cached version of page? at webapps.SE.
If you have the link, you can also check whether some version of the post was not saved in Wayback Machine.