Again you have to catch the defect yourself before you use the phone. And if you "lose" your gasket go find it and fix it. Your going to have to prove the water got through a case in the original posters dilemma and through the SIM tray before you opened it. The only real way your going to figure it out is by inspecting the SIM tray first. Anything could have happened to the SIM tray before water got in. Hell if you already had opened it before without fully closing it can cause water damage.
I'm literally talking about the phone coming out of the box with a defective SIM card tray. It's not that hard to grasp what I'm referring to. You just keep spinning it.