Since the gas lid does not "lock", it can easily be accidentally opened if you press against it.
Happens sometimes while washing the car (with doors locked), or maybe someone you know is playing a practical joke on you.
I think I did bump into it once but I keep finding it open ? Matter of fact since I made the original post I went out to get something out of the car and it was ajar again !
I’m wondering if the spring is a bit strong and maybe with some time it will break-in ?