If I asked a question on ServerFault but it was closed there and moved to SU, how do I claim the newly migrated question? The specific question is Laptop Display Goes Blank
Go to your preferences (your name at the top of the page) and click the accounts tab. There you should see something about merging accounts. After the merger you will get ownership of your migrated question.
If that doesn't work out for you just mail email@example.com with links to your accounts and ask that they be merged. But it's quicker if you do it yourself.