Help! re 910XT data loss but seems to be there somewhere.

I ran my first 91k race the other day. When I was running a message popped up something about deleting old activities which I just hit enter and continued to run being in the middle of the race. The race took over 18 hours in sub zero temps and some high altitude and the battery was running low when I finished I remember resetting the activity when I finished but don't remember turning off the watch so it probably just died. When i turned the watch back on with a bit of charge the activity was not there nor was the one from the previous day. I returned home and charged the phone completely and then it transferred data for a long time, one of the activities (sadly not the race) appeared. I tried to manually upload and it says there is an activity on the device from the day of the race however it just says uploading but doesn't stop after an hour I gave up. The activity does still not appear on the watch itself. Any help or any ideas would be greatly appreciated this was a big deal for me personally and not being able to record it really sucks as I am sure everyone can imagine. I use a mac to download all my activities. The watch is new and under warrantee still in fact I bought it because of this race!