It has been noticed that some images are missing sometimes in threads. This is generally caused from users embedding images from a third-party image host like photobucket and then somehow the images are removed from the host.
You can see an example here....
http://olivertraveltrailers.com/topic/dexter-single-axle-suspension-kit-legacy-elite/
Keep in mind that if you delete an account from an image host or remove an image, it will also remove the image (or post an image not found) anywhere you have embedded it.
Just wanted everyone to be aware. Thanks!