Glass back just cracked like that!!

Got My new edge+ yesterday. I was happy as a child playing with it all day. In the evening I was ready to go to sleep, the edge was a bit warm of using it, not hot but just warm. Didn't play games or so, just usual apps installing, browsing, YouTube, etc... I wanted to check something on my surface pro which was on the kitchen table. I layed my edge next to it on the table on its glass back, no cover. While I was busy on my surface I heard strange noises, like things cracking. At first I couldn't see where it came from, It lasted several minutes. After I was done I took my phone to put it on the charger and I felt something strange on the back. DAMN, the entire back cover was cracked, not just a bit but scattered! Just like that! I went crazy, really. It seems that the metal band just crashed the glass back cover. I suspect the the colder surface of the kitchen table shrinked the warm metal band of the edge and so crushing the glass somehow.... How on earth am I going to explain this in the store where I bought it? They will say I dropped it, but I didn't for sure. You can't see any dent or scratch proving that. I will see how it goes tomorrow, will keep you posted. I'll make some pictures as well and post them here. This Is clearly a manufacturers faulty construction. So beware of warm devices on a colder surface!!