Unfortunately in my Lenovo laptop this problem happens sometimes when Windows updates automatically its OS or the Defender security database. I suppose that some Microsoft OS patch impacts in some way the Lenovo integrated camera driver and for this reason it stops working and it disappears from the Device Manager.
Here is the solution that I usually follow when this happens:
1) restart the computer (obvious mandatory first step in the IT world)
2) if after the restart, the Lenovo integrated camera still doesn't work (for example, doing a Skype videocall) then check the Windows privaty options as there is a specific Webcam option that must be enabled in the "Let applications use my webcam" setting (restart the computer after enabling it just in case it may be needed and it should finally work)
3) if after the restart it still does not work, open the "Device Manager" administrative Windows tool and check if there is some "Integrated Camera" device in the tree hierarchy (usually it should appear under "Imaging Devices" or directly under some specific "Cameras" entry), so if there is one, jump directly to step 5
4) if there is nothing in "Device Manager" about the Lenovo integrated camera, probably it may be hidden, so you have to activate the "View -> Show Hidden Devices" in the Device Manager menu options, so this should allow finally to see the Integrated Camera appearing in some kind of semi transparent way that means that Windows kernel has "disabled" it
5) so now you can try to "update driver software" option in order to reinstall the Lenovo driver although in my case this option usually does not solve the problem as I usually get a message similar to "hardware not available" or "latest driver is already installed properly", you can also try to "disable/enable" it but again usually in my case this never works and I always get the same previous message, so the only option is to "uninstall" the integrated camera to remove it totally from the Device Manager and then you have to power off your Lenovo laptop and restart it
6) when the Lenovo laptop restarts, Windows OS will automatically reinstall the Integrated Camera driver correctly, so after the system is correctly restarted you can open again the "Device Manager" tool and you can check that now the "Integrated Camera" appears again and this time it is perfectly enabled meaning that Lenovo drivers have been correctly reinstalled and activated, so when you use a webcam application (like Skype) it will finally work again perfectly
Hope this helps you in some way.
Cheers!