A method can be used for detecting a potential presence of an object by a reader capable of mutually communicating via a contactless communications protocol. An antenna of the reader transmits a magnetic field on a carrier signal having a sub-carrier modulated by a first data sequence. The modulated sub-carrier is non-interpretable by the object. The antenna of the reader receives a signal resulting from the transmission. The reader demodulates the sub-carrier of the resulting signal so as to extract a second data sequence from the resulting signal. The first data sequence and second data sequence are correlated and the potential presence or absence of the object is determined based upon the result of the correlating.