Correction notices are automatically deleted from your message box when you respond with "I have corrected" or "Not an error".
The thing to do is, reply before you hit either of those buttons. 
But that doesn't help you right now, unfortunately. Do you remember the name of the helpful someone you wish to contact? If so:
From your main page, click on "List/Edit my games". Up in the address bar, there should be a lot of nonensical gibberish that ends in "=Vikan". Replace your id with helpful dude's id (eg. if you wanted to contact me you'd end with "=LadyCaitriona". Make sure that you don't change the REST of the address!)
This will bring up a list of helpful dude's quizzes. On any of them, click "Send Msg to Editor".
This'll only work if helpful dude has actually MADE some quizzes, though. If he hasn't, I don't think there's anything you can do.