See here you have to first save the scrolled position of tableView i.e. contentOffset of tableView and then reuse it when you are coming back to tableView.
1)When and where you will save it :
When : At the point, when you are drilling down to detailViewController save the contentOffset of tableView
How : float verticalContentOffset = tableView.contentOffset.y;
2) How will you set tableView back to the same scrolled position :
[tableView setContentOffset:CGPointMake(0, verticalContentOffset)];
Hope this will help you.