Hardly a bike broken in half, but I get your point, it's a new bike and all. That looks more like the bike was ran into something, like a overhanging shelf bracket or something crazy like that. I don't think that's a wrench slip. If they won't for some reason replace the entire stem then politely ask them to replace at least the removable face cap. That's really the only potentially affected area. The stem itself would be fine with a smooth over and touch-up.