Hi MypicsCloud,
Welcome to the Apple Community.
Apple support have an article online that may help,
"If you're missing photos or videos in the Photos app"
Says:
Check your Recently Deleted folder ... see the steps for recovering photos in the aetoicle (link below)
NB: Also says: If you hide photos and videos, you'll see them only in your Hidden album, so it might seem like they're missing. But you can unhide your photos and videos whenever you want. With iOS 14, you can hide the Hidden album so it doesn't appear anywhere in the Photos app. So if you're missing photos or videos, make sure the Hidden album is turned on so you can see it.
Complete article:
https://support.apple.com/en-us/HT205912
or for iCloud:
When you delete a photo or video from Photos on iCloud.com,
it’s also deleted from all your devices that have iCloud Photos turned on.
If you change your mind, you have 30 days to recover it before it’s permanently deleted.
Recover photos and videos
- In Photos on iCloud.com, click the Recently Deleted album in the sidebar.
- If you don’t see the sidebar, click
. - Select the photos or videos that you want to recover and then click Recover.
Complete article: https://support.apple.com/en-au/guide/icloud/mm08b49040b5/1.0/icloud/1.0
Else:
You may have a back-up of your iPhone (on iCloud, computer, external storage), where you can recover the missing photos.
Hope this helps :-)