iphone home screen question

I have been experimenting with your free version and came across something weird. I added my site to my iPhone home screen and noticed your mobile joomla icon appeared. I then learned that I could overwrite the icon image in the iPhone template. I did this. I then deleted the icon from my home screen, cleared the cache in safari and added the icon again. It was a success until I opened the Web app and closed it. Once I closed it, my nice new icon turned into your mobile joomla icon. Is this because I am using the free version as opposed to basic or pro?