The P1's passive preventing stealth is still active after it is destroyed.

Whenever fighting a fleet with the Punishing One, it's passive that preventing stealth and applies breach to a ship attempting stealth is still active for ships that are reinforced into the battle after it is destroyed. Any ships that are present when it is destroyed are able to stealth as they would normally, however, any reinforcing ships that become stealthed are prevented from doing so and receive breach as well. This especially affects ships that have stealth as part of their reinforcement abilities, such as the Phantom and Bistan's U-Wing. But any reinforcements are affected by this.