In my code, I can get selected item from grouped LLS like this:
private void LLST_Hold(object sender, System.Windows.Input.GestureEventArgs e)
{
if (LLST.SelectedItem != null)
{
ItemType item = LLST.SelectedItem as ItemType;
// do some stuff
}
}
If it's not working, maybe you can show some more code.
EDIT
Note also that hold event doesn't select it (that's maybe why it's not working in your code as you expect it). Check if hold works after selecting item with a tap first. You can read some more here.