Little is known about the experience of family and friends when a young adult goes missing, less is known about how siblings make sense of the experience. Police assistance to locate the missing person may be sought but there is little recognition of going missing or missingness as a social issue, and there is little or no adequate social response to the needs of those left behind. This paper links knowledge of siblings, loss and grief to an understanding of this phenomenon. It presents the methodology and findings of an exploratory, qualitative study into the experiences of nine adult siblings of long-term missing people in Australia and presents the themes drawn from their accounts. The themes are briefly elaborated using direct quotations from participants in the study and represented in a diagram. The paper seeks to develop greater understanding of the inter-relationship between missingness and other social issues, to give voice to the views of participants and to encourage practitioners to engage more purposefully in work with family and friends affected by this issue. Some implications for social work practice are presented.