There have been many questions that I helped close where I am not shown in the closed as ... by ... line.
Is there a reputation line or some other requirement at which you start being shown in the list? Or maybe if you voted to close for a different reason you aren't shown?
You get credit once you get the Close Vote privilege, which happens at 3,000 reputation. Before that, flagging for closure just puts it into the Close Vote queue, so that those that do have that privilege can review it.
Once you get 3,000 reputation, note that flagging to close a question doesn't generate a flag anymore; it just uses your close vote for the question.
