What sort of lockscreen are you using if the display is coming unlocked in your pocket? Back in 2011 I used one with an iPhone-style slide to unlock (and no other security) and that would sometimes do it, but it's the only unlock style I've ever met that did unlock in the pocket, and then only rarely.
thanks for the tip about other launcher.  I will give it a try.
As for the lock screen,  use the pin number I do have it and this is the most frustrating.   If I set my phone in my pocket to fast, before the lock, then it never locks.  What usually give it away it's the temperature of the screen.  But by then, I have called people, rearranged my screens.
In addition some other app like the music player will work even if screen is locked.  So I am walking and suddenly the music starts.
But if I need to answer a phone call then by the time the screen is unlocked, the caller is on my voicemail.
It happens more than twice a week.
Yes I would love a freeze layout option.