Of course, if you want to believe it's ME Terrorists and that the government is covering it up, I suppose you could believe that the card was never actually dropped by the shooter. I go for the simpler view.
The Tarot card is a red herring meant to create confusion and conceal the killers true identies IMHO. The words "...I am God" are likewise meant to confuse and distract from the killers true indentity.
Do you think that the rambling, poor pennmanship, spelling errors, and grammatical mistakes found in the Anthrax letters are indicative of the scientist that weaponized the Anthrax found inside? Of course not. The point is to create confusion and a media circus.