The Archive of the Accademia di San Luca in Rome is a well known address to all scholars and students interested in XVIII century architecture. Here, instead of describing what is possible to find, we point on the missing documents, that we group in three categories to whom we assign the following titles: reticence, deliberate omissions and loss. Under the category of reticence we have listed some contrasted elections to the academic body that have left no documents; under the category of deliberate omissions we present a unofficial story of some of the Concorsi Clementini. Finally, under the category of loss, we list all information available on the opinions requested to the Academy about current architectural enterprises in XVIII century Italy.