I would say upgrade to 4.2 and it will no longer be needed since it is built in now.
However you more than likely upgraded your site or changed your style or edited/replaced the wrong template. Also, make sure you check in the admincp > plugins & Products > Manage Products to see if it is still there and not deactivated.
Lastly, and probably the fastest, just reinstall the mod and make sure when importing the product in your admincp that you select the 'overwrite' check box.
Here is the mod I think you are referring to:
https://vborg.vbsupport.ru/showthrea...iewed+a+thread
Hope this helps,
-Jason