HP laptop built-in webcam disappeared between Xubuntu 16.04 and 18.04

[MR ZenWiz]

I have an HP8740 laptop (I know, it's old, but it has 1920x1200 res on
a 17" screen that I like a lot).

I upgraded it from 16.04 to 18.04 in July 2018 after the LTS .1
release came out.  I recently had a use for the webcam that is built
in, but the entry in lshw disappeared between the releases.

Here is what lshw showed for the device in 16.04:

                  *-usb:2
                      description: Video
                      product: HP Webcam [2 MP Macro]
                      vendor: Chicony Electronics Co., Ltd.
                      physical id: 5
                      bus info: usb at 1:1.5
                      version: 85.54
                      capabilities: usb-2.00
                      configuration: driver=uvcvideo maxpower=98mA
speed=480Mbit/s

Now there is nothing at all for that device, and the output format has
changed a bit (the "*-usb:#" format is gone).  The roughly
corresponding part of the output simply does not contain any entry for
*-usb:2.

Is the camera dead and how can I tell?  Is it possible I disabled the
camera and it died or at least refuses to respond, and if so, how can
I fix that?

If I hook up an external USB webcam, that works fine but the built-in
is still invisible.

I looked in Google and found some info re HP webcam issues, but none
of it seems to apply to this specific model of webcam.

Thanks.

Mark