In 1893, Australian naturalist P. H. Wainwright traveled to Mauritius to investigate a series of unusual skeletal remains reported by local laborers. His expedition uncovered evidence suggesting that the dodo had persisted decades beyond its accepted extinction. The Society secured Wainwright's journals, photographs, and recovered specimens, sealing the collection pending further review. Portions of the expedition have now been released under Charter Article V.

Following the reported recovery of unidentified debris near Roswell, New Mexico, in July 1947, the incident and its recovered materials disappeared into military custody with remarkable speed. Through channels the Society has never publicly acknowledged, a small number of artifacts and supporting documents were recovered before the collection vanished from official view. Catalogued as Dossier 001: The Roswell Transfer, the surviving materials include biological specimens, technical artifacts, and contemporary documentation of uncertain provenance. Only selected portions of the dossier have been approved for public release at this time.