I have a 2011 and it has happened to me at least 10 times. Once I was paged in the gym that a BMW hatch is open. I have written BMW USA and checked with two dealerships to see if I could disable the button on the key fob but they can't do it.
It is dangerous if you leave something of value in the truck and it opens, they should fix this problem as simple as making a two click function. If they don't fix the problem my next SUV will not be an X5 I like the truck but this puts added stress on one.