  Projective (Von Neumann) Measurement of an operator (i.e. a dynamical
variable) selected from a prescribed set of operators is termed unrecorded
measurement (URM) when both the selected operator and the measurement outcome
are unknown, i.e. "lost". Within classical physics a URM is completely
inconsequential: the state is unaffected by measurement. Within quantum physics
a measurement leaves a mark. The present study provides protocols that allow
retrieval of some of the data lost in a URM.
