An international network of/for intelligent organisms
That's slimes for you. They also rejoin quite readily. If the food is fresh, maybe it's little dry, if it's been in there a few days it might have a touch of yeast growth putting them off.
It's just as likely there's no good reason for it - you can rely on physarum to go the wrong way down the maze, escape, die or host of other things that you didn't want it to do.