Watch face (digitizer) fell out. This happened after a flight. When I landed, I checked the time, got off the plane and walked directly outside, checked my watch again and saw the face missing. This was all in the space of 10min walking from the plane to the outside shuttle area at LaGaurdia airport. I did not hit the watch on anything and felt nothing at all. Initially, I went to Apple as I had AppleCare+ and they said that since I did not have all the parts my AppleCare+ was void and they wanted me to pay $700 to fix it. So, I ordered the part from ifixit.com, pieced it all together. I wasn't able to press the face back into place. I went to Apple in the mall near me and told them my watch face keeps popping off. The Genius Bar guy looked at it and said that its because the battery is swelling and they would replace it , no charge, no problems. So, essentially it cost me $225 instead of $700 to fix it and going through all that trouble I will wind up with a new watch anyways, but I'll be assured that it will be waterproof again. At least I know that I got the watch to turn on and that felt good.
I got the watch to work, so it went very well.
I could not find how to get the watch face back in place, I think you might need some sort of press device. The teardown video was very informative. I was able to figure out the re-placement of the gasket as that is not in the video. I wound up finding out that the watch face blew out but the outer ring of the digitizer was left intact. I did not see the damage happen and I also did not hit it on anything, that was the weird part.