What dictionaries did you check? Did you check the one this tournament was using?

Words don't have to be English, they have to be listed in the book the tournament uses.

http://www.anagrammer.com/scrabble/katti

    In which Scrabble dictionary does KATTI exist?

    Scrabble (US/Canada)     No
    Scrabble (UK)            Yes!(9 pts)
    Official Scrabble (OSPD) No
    WordFeud                 Yes!(9 pts)
    Words with friends       No
    Hanging with friends     No
    Letterpress              Yes!(5 pts)
    Lexulous (US)            No