Single Strike Roar - Pokémon Rulings Compendium

Can I use Houndoom's "Single Strike Roar" Ability to search my deck for the special energy card Impact Energy?: No, you cannot. Single Strike Roar is only able to target a specific card named "Single Strike Energy". Although Impact Energy is a "Single Strike" Energy card, it is not "Single Strike Energy".

Source: Chilling Reign FAQ; TPCi Rules Team (2021-06-17)

Can I use Houndoom's "Single Strike Roar" Ability if all four Single Strike Energy cards are in play or in the discard pile?: No you cannot. Since the location of all four Single Strike Energy cards are known, there's no way Single Strike Roar would be able to find one during a deck search.

Source: TPCi Rules Team (2021-03-25)