There are couple of ways you usually see a widget linked anywhere.
One is in another widget the script contains something like getWidget to include another widget inside it.
Another place are the instances inside pages. Inside a page you have rows that contain instances and instances have a reference to a widget. sp_instance contains all the instances and the widget field the widget.
So in your case you can start by checking the pages you're working on or go directly to sp_instance and search for the OOB widget. If changing those don't help then you'd need to query widgets and try to search ones where the script contains the widget id (not sys id) of the OOB widget.
