It might be a connection issue with the display. Have you already dismounted and remounted it?
Pay attention to Step 9, the plastic clamps secure the connection just like the screws do.
First and foremost, the phone needs to be all dry. Water ingress often does not kill a phone instantly, but can still do so days or weeks later.
P.S.: The battery can discharge much quicker in cold weather. Once the phone is all dry, you might need to charge first.