I've proposed the following new custom close reason for here on Meta.Webapps:
The problem described here can no longer be reproduced. Changes to the system or to the circumstances affecting the asker have rendered it obsolete. If you encounter a similar problem, please post a new question.
This is a direct copy of the one on Meta.StackOverflow (sorry Meta.StackExchange).
If we think that it's a good idea then it can be activated by another moderator.