If the USB connection PID and VID are registered to VISA (you can use the Measurement and Automation explorer to do this), the VISA FindResource will report it, along with all other VISA resources. You can use a selection mask (such as USB?*) to find just the USB entries. This doesn't find every USB resource attached to the computer, but it is useful for finding resources that are VISA accessible.
If the device does not have the VID and PID registered to VISA, it is hard to see how you will use it?