Here is my flight log:  http://www.phantomhelp.com/LogViewer/L0UKKIGOU4LM5F3228BO/

Right at the end of the log the app disconected, but I still had connection with controller, but no GPS and RTH wouldn't work. (so I safely landed visually).  It scared the $#% out of me.  Upon reading in to this, it appears some others have had some similiar issues, many with far more unfortunate outcomes.  I noticed I need a firmware update, maybe that will help keep this from happening again?  Let's say it did happen again with the Mavic in still n the air, what would happen if I closed and reopened the DJI app?  Is it possible to reconnect the app when the Mavic is in-flight?  

You can run the MP without app as long as you are in LOS. You can even turn off the phone and app and it won't affect the MP.

So always stay in LOS, better be safe than sorry...

This has happened to me a couple of times....  Let go of the sticks to halt the Mavic and restart the app.  As mentioned, you can fly without the app, but it's much nicer with it