The best thing that I can offer here is:
1. Go to OPTIONS
2. Scroll to find SECURITY OPTIONS and click
3. Click on GENERAL SETTINGS
4. Then either: a. SECURITY TIMEOUT: change to 1 minute (ie. locks the keypad after phone is idle for 1 minute) or b. LOCK HANDHELD UPON HOLSTERING (ie. placed into its leather/leatherette case): change to yes.
5. Save changes.
Hope this helps