If a photo you expect is not in a tour, the usual cause is that it was not selected in the storyboard. Open the draft and check the scenes: photos are chosen deliberately, so one you never picked will not appear.
If a photo is missing from a property, check that the upload finished. An upload interrupted partway leaves the rest of the batch in place, which can look like the set arrived when it did not.
If something you know you created is not where you expect, look in your Media Library. Everything generated stays there, and a tour or edit is reachable from the Library even when you cannot find it from the property.
If it is genuinely gone rather than misplaced, report it and say what it was and roughly when you made it.