Even if you used Matan's modified hildon-desktop to stop desktop widgets moving around, if you're not locking your device before putting it in your pocket then you're asking for trouble. You could easily click on one of the widgets and start loading apps etc. Really, you need to get into the habit of locking it before putting it in your pocket, or re-enable the auto-lock.

Personally I use the auto-lock, but if I want to keep the device awake I keep the keyboard slid out. That way a single tap of the screen will wake it up, but if I want to put it in my pocket I would slide the keyboard shut which will cause it to lock after the timeout.