To make sure that the clutch switches are properly installed check if your cruise control works. While the switch they would have replaced would have been the start switch that checks for the clutch being full down... There is another switch at the top that maybe they messed with. The top switch is what engages SMode in cars that have it, and also shuts of cruise control when you push the peddle down. If that switch isn't making correct contact, s mode will work normal (for several days until it eventually notices and SMode warning comes on the multi gauge and shuts off until the switch is pressed/reset), but cruise control will never work because it thinks the clutch is partly down.

Its highly unlikely that the car removes power when the clutch is down, but god knows with all the random stuff Nissan programmed in this thing. I am just reaching into the darkness for random ideas related to the area of the car that was last worked on.