When you see a little lightbulb ( )in the row of icons underneath the thumbnail of one of your images, it means that a registered buyer has put that image into a lightbox.
Fantastic, you may think, and so it is, but that doesn't always mean a sale has been made. Picture researchers create hundreds of lightboxes which they pass around to clients. They will never go back and delete the lightboxes they've created, so that little bulb just stays there.
It doesn't prevent the image being added to a new and different lightbox. But there is no additional notification.
In this latest version of fotolibra the lightbulb icon will be deleted automatically after it's been glowing for 6 months, as the chance of a sale being made through that particular lightbox after that time is remote.