There are already a lot of questions here on Meta about users deleting their questions promptly after getting an answer. It happened to me twice this weekend. (I even thought they were the same user, because it was on the same day and the topic was the same: metric spaces. In the end, it was two different users. I was surprised though to discover that they were not new users at all, both with about 1k rep).
Anyway, I was told in this comment to flag any post of mine (I couldn't flag the original question or answer, because the whole page was unavailable) for moderator attention, and explain it, which I did, and both questions were undeleted rapidly.
However, one of the users deleted the same question again. I haven't found anywhere, in any of the several questions I linked above, what I should do in such a situation.
I understand that users should have the right to delete their own posts, unless doing so would also delete content that's helpful to the community. I also understand that I'm not the one who should decide whether my answer is helpful of not (after all, it had no upvotes, and that's why the user was able to re-delete it). But still I'm not comfortable with just letting this be.
In the end, I would like a recommendation about what to do upon (re)deletion of questions with an answer of mine. Should I keep flagging forever until the user stops deleting it? Is it better to post this kind of request in the "requests for reopen and undeletion" thread? Should I leave him (and the moderators) alone if he insists in deleting his post?