The Belgian Royal Institute for Cultural Heritage (KIK-IRPA) is a scientific institute responsible for the documentation, study and conservation of cultural heritage. The backbone of its activities is partially defined by its historic photo collection, of which 4% had never been catalogued until recently. Officially non-existent, over time these photographs had become as ghosts in the collection. Facing a high degree of disassociation, a specific methodology in order to retrieve essential metadata (e.g. author, subject, etc.) was developed. Using traditional approaches such as comparative studies, looking at the photographic documents as primary material sources, and using new digital technologies and (internet) tools, it was possible to reinstate these images not only in the photo library of KIK-IRPA, but also as cultural heritage in the digital world and beyond. Following a hibernation of more than a half-century, a bright future now awaits these once forgotten photographs.