Q: is there any way to lock an IPAD app? by lock, I don't mean password protect.  My toddler is constantly scrolling out of her apps and this causes frustration as she spends all her time bringing the IPAD back to me to get back in to the app she was playing

This may help: iOS: Understanding multitasking.

If you turn OFF multi-taskng, your toddler won't be able to "swipe" between Apps.

I don't know of any way to disable the "Home" button though.

It's a simple ipad setting; go to setting-general-guided access, then switch the guided access to "on" then set your password and that's it ! When your child is using an app triple click the home button and hit start on the top left corner and your child won't be able to get out of that app. Hope this was helpfull for you :)