I am assuming you are using GUIDE in MATLAB R2013a to creating your ListBox. Below are the steps I used to create a ListBox where I was able to select an item by searching for it:
1) On MATLAB command line and type "guide".
2) Drag and create a "ListBox".
3) Double Click on ListBox to open 'Property Inspector'.
4) In the 'String' property , please click the List icon on the left of the pane and fill some default values to appear on the list. For demo purposes I am using : Apple, Ball, Bat, Call, Cat, Dog, Doll.
5) Save the FIG file and that generates a MATLAB script file with callback functions to the figure and ListBox.
6) Run the script using the "Run" option in the MATLAB script or click the "Green Play Button" in the GUIDE GUI Editor.
7) To search for items in the list; First, Click on any random item on the list box and then type the initial letters of the item you want to search. The item if present, will be selected.
I have also attached the code to demonstrate that. This did not give me any issues.
If you are still having trouble then you can submit a service request at the link below:
Hope it helps.