Waterline trouble

After a main waterleak underneath our attached garage we decided to put in a new line. We contracted a local plumbing company to do the job. The new water line goes up within the garage wall into the crawlspace of the garage ceiling, then follows diagonal into the crawlspace of the main house and down into the kitchen, where it attaches to the old line. This was done last March, and has been paid in full.
About 2 weeks ago, an about 10x15 foot section of the garage ceiling collapsed suddenly. It is exactly the section where the new water line runs within the ceiling. Now it became apparent that the line is not secured to the studs and was just laying on the ceiling panels. We assume that the vibration of the water line "knocked" the gypsum panels loose over time.
Can we hold the plumbing company responsible for the damage?

Based on what you say here, you could file suit against them (or at least threaten to do so) in small claims court or in regular court