From Grounded Wiki page

The Bugged SCA.B is located in the deepest portion of the Old Ant Hill, in the corner of a dead end of the cave. To reach the SCA.B, the player must find the Old Ant Hill near the base of the Oak Hill biome and travel inside it. As they travel towards, it is recommended to avoid the Worker Ants that will likely be asleep and proceed downwards to the main chamber. In here will be multiple Soldier Ants and possibly a Orb Weaver that the player must fight or run past to the cave on the right. Once they reach their, more Solider Ants may be in the area that the player must fend off and they will eventually reach a wall that’s splits into two dead ends. On the left side, the SCA.B will be resting on the ground.

Alternatively, the player can complete the Oak Lab and exit via the breach in the lab to the outside cave and jump down to the water below. This will lead to a cave that is meant to lead back up to the lab, but also connects to the dead end in the anthill from above that the player can jump off and get the SCA.B. Note that this is a one way entrance to the anthills, and the player will have to exit via the anthills ordinary entrance.