2021 SUBARU CROSSTREK — POWER TRAIN:AUTOMATIC TRANSMISSION:LEVER AND LINKAGE:FLOOR SHIFT

I just recently had my car come out of park while running at the top of a steep hill. I had stepped out of my car to deliver paperwork to my client. I walked to and from my car approximately 75-80 ft. As I was approaching my car I heard a clicking or a release sound then it began to roll. I wasn’t close enough to stop it and it rolled down a neighbor of my clients driveway and eventually rolled over landing against a tree. When I arrived at my car it was still running. I have awd and I noticed the tires in the air were not turning as they should have if it was in drive. My car was obviously totaled. How do I have someone check my car to see if there was defect that caused it to come out of park? I must say I forgot to set my handbrake. But I feel the car should not have come out of park regardless. Could it have been the front axle shaft or anything else?