I'm real sorry but there isn't a lot of info out for this device. Here's a short tear down guide. I realize he didn't go into the button part of the watch. But hopefully it'll help you safely get into the phone and get that button secured. If you're not a super tech savvy person. Maybe you don't want to start messing with your brand new smart watch. If you are. Take lots of pictures and make a guide to help other people here with the same problem!
http://m.youtube.com/watch?v=5WzGC0786U0