Battery die before end of round - golf stats lost?

When you ended up powering the watch back on after charging, if you accessed the golf feature did you see a "Resume Round" option alert displaying on screen? That should allow for the round to be saved. 

If the round was saved incomplete then it may be missing the shots or other data due to the watch shutting off abruptly in the middle of the round. You may check and see if any of the shots can be added if any of the holes are showing able to be edited for that scorecard. 

Try syncing your watch via a corded connection using a home computer through Garmin Express and refresh the scorecard list and see if that results in the missing data populating the scorecard. 

If any further assistance is needed, you can also contact Garmin Support as well.