Querying Treeview Items Does Not Working

Code:

string $window = window;
string $layout = formLayout;
string $control = treeView -parent $layout -numberOfButtons 3 -abr false;

formLayout -e
-attachForm $control "top" 2
-attachForm $control "left" 2
-attachForm $control "bottom" 2
-attachForm $control "right" 2
$layout;

showWindow $window;
$a=treeView -edit -addItem "layer 1" "" $control;

and now attempting to query it via :
treeView -q -itemIndex "layer 1" $control
Error : Object not found: layer 1.

second attempt :
treeView -q -itemIndex "" Item $control
''" was not found in the treeview.

how can I learn the item index of item "layer 1"?
this means this control doesnt defined completely and not works %100 ?
(thanks before any suggestions)