Whenever a question is put on hold, the 5 people (less if a diamond moderator is involved) you see are the people who actually cast a vote to close.
In your case, you flagged the question instead, which means you are not one of the five, and hence are not shown.
As for the order in which names appear, it is in order of when each user cast a vote to close. (Here's an old question that explicitly mentions the order, thanks to @MartijnPieters for digging it out.)
For more info on closing, there's the help center page on casting close votes (as already mentioned by @jmort253), and also What is a "closed", “on hold”, or "duplicate" question?.
(Note that while it's true that you need 3000 reputation to cast close/reopen votes on general questions, you gain the ability to do so on your own questions at 250 reputation.)