CS101 Robot Program

On my way to the Computre Lab on the second floor. A bunch of students were making mini LEGO robots for maze solving. All equipped with a fixed Ultrasonic sensor(can compute distance from obstacles like walls) and a pair of wheels and a pivot to rotate. The maze was card board and on uneven surface. meaning the robots couldn't always keep going without often slipping or sliding, leading to changes in orientaion, often messing up everything. This was happening a lot.
The memory is sufficient but not enough to build a map of the maze. The good news is that the uneven surface can only cause the robot to change orientation by a max of 30-40 degrees....Which is potentially recoverable.... the maze is not too big and time is unlimited.

I know that it was simple DFS using the sensors, distance from the furthest wall would do as the depth measure...When you get to a wall pivot Right and left and spot the next furthest wall...

But there was a vey implicit "A starish" behaviour used in the best performing design, even when the search was DFS...Can you spot it!!??