I immediately called my contractor, who called the plumber, who showed up bright and early this morning to locate the leak. The plumber investigated for quite some time and finally called the guys that had been working on the job. They admitted that while they were working, they had removed a cap from a pipe in the bathroom vanity and somehow the water got turned on. They had cleaned up the flood in the bathroom, so that by the time we got home, there was no water in there, leaving an inexplicable mess in the walk-in-closet.
The plumber offered to pay for more Pergo, if I had to pull it up, which later the contractor confirmed was the best course of action. The stuff is meant to go down, but not to come back up. I eventually had to take out 4 rows of Pergo to get rid of all the soaked boards and most of them got severely chipped while I was removing them. It's going to take me hours to replace them. There are three complicated cuts in the last row, approximately 2 easy cuts, and then the T-Moulding for the doorways needs to be trimmed to fit and that can be complicated.
Argh. I was so ready to move on to other parts of the house.