I asked a question here, a while ago. Someone answered my question and actually his/her answer was helpful and I was studying it, but then she/he deleted the answer! How can I figure out who answered? How can I ask her/him to post the answer again?!
Anyone with 10,000 reputation on the site can see deleted posts. You can try asking in an associated chat room if any such users can check who the answerer was and let you know. You can then ask the answerer to consider undeleting the answer.
Alternatively, once you're bringing it up in a chat room, you can simply ask if any of the users with 10,000 reputation can take a screenshot of the deleted answer and post it in the chat room. Then you won't need to deal with the answerer at all.