If the poster used a direct link to the seller store site, it's possible the system is blocking them. We have an issue with people posting items from stores and using direct image links to those stores which results in our users getting TRACKING COOKIES from those stores identifying WHO THEY ARE and WHERE THEY ARE GETTING THEIR STUFF FROM. We have asked everyone many times to use an external image posting site to copy the images to, and to then use those links which are NOT traceable back to the stores they came from. We are cracking down on this, and if our algorithms are correct, you will see many images disappear until they are replaced with proper images links to external image server sources.
I think this is why you are seeing images disappear. It has been an ongoing and serious issue we are trying to protect ourselves and our users from.
AnjaBear