Major goof that should be in the goofs section

I suggest you all pop in the Monsters Unleashed disc and listen very carefully in the scene at the Coolsville Museum, where the gang has donated all of the items and costumes from their past mysteries.

Here Daphne points at a costume and tells its the costume of the Black Knight Ghost, Fred reveals it was their first case.

I guess you can tell what the goof is, the entire story of The Mystery Begins, where this story suddently now is suppose to be their very first case.