I am new to sencha so please bear with me.

I have to create a nested list with data coming from database through a api made in php .
So I created two lists with first list populated with api call and then in item tap function of the second list called the other api and passed the selected data so that accordingly dependent items could be loaded. It is working fine till now.
Now I had both these lists in a panel and I have a back button toolbar in the panel. When I click on back button I reloaded the main page but when I go back to list from the main page this time it goes blank.
The same link first time shows the data but after going back from the back button and again clicking the same link it does not shows the list just the empty page.
Please help.