Randomized Ultra Moon softlock.

[KewlKirby]

I randomized Pokémon Ultra Moon, and sometimes when I encounter a trainer, they will have a Pokémon that has a Mega Stone and mega evolves. Whenever I defeat one, it will say “(Trainer Name) is going to send out (Pokémon that was just defeated), switch Pokémon?” Or something like that, but they only have one Pokémon. I’ve had a Youngster use one, but I walked past him, I’m at the point where I meet Team Skull and you have to fight one of them, but they send out a mega Salamance (?) and softlocks me. The only thing that may solve this is environmental effects like Sandstorm, but I don’t have any Pokémon that know that move. What should I do?