Hi Judegordon1,
Welcome to the Apple Community.
Re: Most of my photos have gone from my iPhone
Seems that if iPhone needs more memory / storage space to operate, some files that can be replaced may be removed.
If this is what has happened, you might want to back up your photos to an external drive, Eg flash drive or portable hard disk.
Apple support have articles online (links below) that may help you.
Learn the difference between your device and iCloud storage,
ways to manage your space, and where to buy more if you run out.
https://support.apple.com/en-us/HT206504
How to check the storage on your iPhone:
https://support.apple.com/en-us/HT201656
How to get recently deleted photos back
NB: Scroll to: "Recover deleted photos or videos"
https://support.apple.com/en-us/HT205856
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Ways to securely store photos.
Transfer photos and videos from your iPhone,
https://support.apple.com/en-us/HT201302
Or
Connect external storage devices to iPhone:
Attach the USB drive or SD card reader to the charging port on your iPhone using a compatible connector
https://support.apple.com/en-au/guide/iphone/iph95baac91f/14.0/ios/14.0
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Re: the photo icon has actually gone
How to find your Photos apps icon in App Library on iPhone
https://support.apple.com/en-au/guide/iphone/iph87abad19a/14.0/ios/14.0
If needed:
How to move apps and widgets on the Home Screen on iPhone
https://support.apple.com/en-au/guide/iphone/iphd2fc8ce30/14.0/ios/14.0
Hope this helps you :-)