Could I use a Poké-POWER, Poké-BODY, Attack, or Trainer to search through my deck for a particular card if I already know that card is not in my deck (i.e. using Energy Search if you know there are no basic Energy left in the deck due to previous unsuccessful searches)?
Yes you may, but if done repeatedly a judge may evaluate whether it's being used legitimately or merely as a stalling tactic.
Source: PUI Rules Team (2005-12-08)