Water damage at any scale strikes fear and loathing in the hearts of homeowners. A pipe leak is often messy to clean up, and it also damages a builder’s reputation for delivering quality work, putting everything else about the job under suspicion. Not to mention that the owners likely Googled “mold” (soon followed by “lawyer”) before they even called the service department.
Assuming a simple leak (as opposed to a systematic installation problem), it’s probable that a subcontractor following the plumbing rough may have punctured a pipe while tacking down some flooring or hanging drywall. The leak would have been undetectable prior to water service and even after that might have been too small to cause much damage.
But, over time and with the inevitable movement houses make during seasonal changes in climate, the opening would inevitably expand, its water volume increasing from perhaps a drip to a free flow that would affect water volume and show signs of damage on floor, wall, and/or ceiling surfaces.
As with all callbacks, the key is a fast and purposeful response. The service tech or plumbing contractor should be prepared to visit the house within a few hours (at the most) and not only diagnose but also perhaps repair the leak at that time. Cleanup and repairs can be negotiated later, if in a timely fashion.