I can confirm that I've had the same thing happen to me.
I was regularly coming out of the plan and back in to make sure it saved and it appeared to be working.
After a few hours the iPad died (battery) and when rebooted all my modifications - about 2 hours worth - had gone and its gone back to a previous state!
So it may well be saving on each change but its not persisting the changes to the same place that it gets the plan from on initial boot up..
Which product are you referring to?
Saving a plan is done automatically to your device after each operation you perform. The only reasons a plan will not show up is if you restored a backup of the device or you're simply inside a folder, in which case go up one level to the plans main screen and you will see your plan.
We always recommend to backup your plans to Dropbox or email, and it is easy, fast and simple to do with the app - simple tap the little arrow on the plan thumbnail and select Share.