That is the reason you could not edit a photo. Joining allows a Member to edit/delete/arrange, etc photos. The site Manager Ken may be able to help you retroactively if provided the URL of the photo in question.
When I started uploading photos here in 2005 when the site was relatively new-I had about 49-50 photos uploaded before accepting an invite to join. ken was able to move all my photos then to my Home Page, which I further then re-arranged. I'm still adding and re-arranging aircraft and airport photos.
Welcome aboard!