How many missed triggers are necessary before you begin to have Game Losses and/or DQs?
The same pdf referenced contains some text that shows the escalation of warnings on page 7 (2paragraphs before the start of the 'gameplay error - missed trigger' section):


  A third or subsequent Warning for a Game Play Error offense in the same category should be upgraded to a Game Loss. For multi-day events, the penalty count for these infractions resets between days.