In 'The Arctic Experiment', Mulch on page 207 asks Artemis, (and I quote),

" 'Who are you, hu... boy?' "

Close quotes.

Yet in 'The Artemis Fowl Files', in the novella 'The Seventh Dwarf' which is supposed to happen BEFORE 'The Arctic Incident' (page 116):

" 'I know who you are, Mud Boy,' said the dwarf [Mulch]. 'Your name is Artemis Fowl.' "

Direct quote, from page 127 respectively.

I checked to see if Mulch had been mind-wiped during the time between the stories, but no...