When was the last time you saw those pictures? What has happened since then-- did you do an update of the operating system, or did you use some sort of "cleaning" app?
What operating system are you using on your Mac? The most recent one is macOS 13.2.1 Ventura.
Are you using iCloud to synchronize Photos on your Mac and on your iPhone? if so, have you looked to see if your pictures are at iCloud.com?
Have you looked in the Recently Deleted section of Photos?
If you haven't done this, try using a Smart Album to search for pictures of Iceland. Or use the search field in the upper right of the corner of the Photos window:

(I haven't been to Iceland-- I'm jealous!)
Let us know....