Piper tried not to panic - or, rather, he tried to shove the panic down. He followed Daniel down the hall to the bedroom, and he hovered outside the bathroom, close enough to see and react, but not close enough to crowd.
The fact that there was what appeared to be an xacto knife in the bathroom? That made him panic. he shoved it down, down, down, and he very calmly followed Daniel back down the hallway, a silent, protective shadow.