Thank you for the posting those pictures. Just to be sure, when you checked for the LEDs, did you have the 3pi powered on (both blue power LEDs should be lit on the 3pi) and the LCD removed? If not, can you remove the LCD from the 3pi, load the 3pi-linefollower example code (again), and verify that the 3pi is powered on before checking for the IR light from the sensors?
There is a MOSFET on the 3pi that is used to turn on and off power to the IR emitters on the line sensors, so if that was damaged, they might all not light. Could you post a clear, close-up picture of that MOSFET (marked by the red circle in the picture below)?