WHY do others then go on to tell you what you should have done when you have all ready stated you know now it should have been registered.

Have a look at the buyer feedback left for others to see if they have a habit of this and also do a search on their purchase history to see if there is a lot of purchases they have not yet left feedback for.

It will be time consuming but if you can see a pattern then you might need to go to the online fraud police about it.