Stop reloading of web app launched from iPhone Home Screen
Solution 1:
I just found this related question on SO: Stop native web app from reloading itself upon opening on iOS
As it seems it's a limitation of Safari, a proposed solution is to persist your web apps state using Javascript and HTML5 localStorage. When your web app is launched, check for the persisted state and load it if available.
You can read about using localStorage in Safari here: http://developer.apple.com/library/safari/#documentation/iPhone/Conceptual/SafariJSDatabaseGuide/Introduction/Introduction.html#//apple_ref/doc/uid/TP40007256-CH1-SW1
Hope that helps you. At least it did for me, as I had the same problem as you. :-)