2000 Honda Civic transmission problems

Vehicle was driven and parked on sloped driveway in 1st gear with parking brake engaged fully and engine off. Driver walked into house came back 5-10 minutes later. Vehicle had rolled down hill and hit transformer. When vehicle was opened parking brake was fully engaged but was not in 1st gear but neutral. We tried to recreate this event. There was no way driver could have left the vehicle if brake was not fully engaged due to steepness of the driveway.

My 2000 honda civic was recently repaired due to a minor fender bender with a curb. The transmission was replaced as part of these repairs with a transmission from a salvage yard. While driving this vehicle, the check engine light came on and after a diagnostics test, the code p0240 continued to show up after being reset numerous times. This light turns on about three miles of driving after being reset.