Mysterious Fossil (LM 79). Mysterious Fossil was in the Opening Hand. But I could not play it as my Active Pokémon. This should be possible.
Game starting
Game type: QuickPlay
Game format: EX Series
Battle started between ATOMISATOR and hrr412!
Coin flip result: TAILS
hrr412 will start
Game setup complete
Between turns
Turn 1 begins
Battle Frontier is now in play.
Between turns
Turn 2 begins
ATOMISATOR drew 1 card
ATOMISATOR played Mysterious Fossil.
Put Mysterious Fossil onto bench.
ATOMISATOR played Mysterious Fossil.
Put Mysterious Fossil onto bench.
[ATOMISATOR]: If there is a Fossil Card in your opening hand, you may play it as your active Pokémon. But I could not. I am going to report this bug.