Recently, a question asked here which I answered has been deleted by the owner and reasked on a (then) private beta site, quantum computing.
I don't think that such a 'manual migration' is a good idea, in particular because my answer to the question got deleted in the process.
For this case, I decided to simply re-post my answer on the moved question, similar to an actual migration.
I didn't really mind, as I'm active on that site as well. So, I'm not asking what to do with that example.
However, I'm not aware of any policy or accepted methods to deal with this situation. So, what should I do if I encounter a similar situation in the future?