iPhone favorites don't sync to LRC - but they did sync to LR on iPhone first - then disappeared ...

I was so happy that all my favorite marks (hearts) from the iPhone photos app perfectly synced to LR mobile on the same iPhone - offline vacation. They appeared as flags in LRM. So I wouldn't have to do the SAME flagging job again when returning home to continue in LRC.  

When I came back online at home and  synced my iPhone to the LR cloud the favorite marks (hearts) i.e. corresponding flags in LR mobile were STILL there in LRM. 

BUT when I turned on my Mac at home one day later and synced the photos to my local LRC - ALL flags disappeard BOTH in LRC and even on my iPhone in LR mobile where they were visible just a day ago.

Is this a bug or what is the problem. So much lost time ... 

Thank you, Hagen