... This solution fails in a situation where searched node's grand parent is collapsed but its childrens are expanded. ...

Please check out the snippet of JS function below.

function FindNextNode()
{
    var tv = ISGetObject("WebTreeView1");
    var searchText = document.getElementById("txtSearch").value;
    if(searchText != "")
    {
        var node = tv.FindNextNodeByText(searchText);
        if (node != null)
        {                
            //node.Select();
            node.ExpandHierarchyAndSelect();
            node.GetElement().scrollIntoView();                
        }
        else
            alert("The search text can't be found");
    }
    else
        alert("Please fill in the search text");
}

I use this JS function to search WebTreeViewNode by text. ExpandHierarchyAndSelect() is called instead of invoking the Select() method. This method, ExpandHierarchyAndSelect(), will expands and selects nodes in a hierarchy.

After hierarchy is expanded and node get selected, invoke scrollIntoView() to scrolls the selected node element into the visible area of the browser window.

This should helps.