Thanks for the quick answer!
What if the the phone was not placed on the starting tile by a human, but instead dropped off somewhere in the maze (possibly also on the starting tile?) by the robot. Would that be considered having multiple robots or would it count as the robot just dropping a part in the maze?
Section 3.4.2 of the rules (“Any parts that the robot loses intentionally or unintentionally will be left in the field […]”) implies that the robot can intentionally drop parts of itself in the maze. The word “parts” in 3.4.2 has been confirmed to include things other than rescue kits (such as objects for orientation) in this answer: Orienteering objects.
Thanks!