Pinsir was encountered at Vermilion Forest. It attacked Ash and Pikachu, trapping them in a ring of large stones. It then went after Go, who threw random objects in an attempt to defend himself, eventually accidentally throwing a Poké Ball and catching it. Pinsir and the rest of the Kanto Bug-type Pokémon Go caught were brought back to the Sakuragi Institute where Professor Sakuragi kept them in storage for Go.
At the Sakuragi Institute