Scan a QR code that is in your phone, not in a 2nd location

You're right, using the phone's camera to scan a QR code that's displayed on the same phone won't work. However, there are a couple of alternative methods you can try:

1. Capture a screenshot of the QR code on your phone and then use a QR code scanner app available on the App Store that allows you to upload images from your gallery to scan QR codes.
2. If you have another smartphone or tablet available, you can display the QR code on that device's screen and use your iPhone X's camera to scan it.
3. Some QR code scanner apps offer an option to scan QR codes from images saved in your phone's gallery. Look for an app that supports this feature and use it to scan the QR code from your saved images.

Apple's native camera app doesn't support scanning QR codes from images stored in your phone's gallery, so using a third-party QR code scanner app might be your best option in this case.