So where is the evidence on Sal?

Hint 1 of 9:

Take a close look around the hot tub room.

Hint 2 of 9:

There's a roll of film underneath a grate on the floor.

Hint 3 of 9:

You can open the grate with the screwdriver that's also stuck down there.

Hint 4 of 9:

The screwdriver is made of metal.

Hint 5 of 9:

A magnet might help you retrieve it.