2007 Pontiac Torrent Water in Trunk

I had parked my car outside for a couple of days and it rained non-stiop. I noticed a large amount of water under the cargo space where the spare tire is at. The dealer said the warranty does not cover leaks after 36K even though I have an extended warranty up to 100K. I do have a sun roof and I can't find any moisture inside the car - help me out on this