Maybe loosing interest before starting? Or the Boss has entered the room?
They did not leave the battle, which made me wondering. I think the game suddenly shut down for them while battling. Canāt think of anything else that might have happened.
Yes, this happens sometimes - but if you want to come back, you can start pogo again and you will land back in the battle - obviously you will lose some time - but this is how this works.
I would say the likely scenario is āBoss entered the roomā 
Orā¦
If you are playing a lot - then you end up bouncing up and down around - having 2:3 or 3:2 results.
This does not give you the access to 4th prise - rare candy.
But if you lose 0:20 - you will be downgraded in ranking by about 100 points - which is enough to get a chance for couple of 4:1 or 5:0.
Of course you can just give up right at the beginning - but it makes no difference - you click start battle and put your phone away and come back after 5 minā¦