  Recently, the principle of \textit{passivity} has been used to set bounds on
the evolution of a microscopic quantum system with a thermal initial state. In
this work, we experimentally demonstrate the utility of two passivity based
frameworks: global passivity and passivity deformation, for the detection of a
"hidden" or unaccounted environment. We employ two trapped-ion qubits
undergoing unitary evolution, which may optionally be coupled to an unobserved
environment qubit. Evaluating the measurement data from the system qubits, we
show that global passivity can verify the presence of a coupling to an
unobserved environment - a heat leak - in a case where the second law of
thermodynamics fails. We also show that passivity deformation is even more
sensitive, detecting a heat leak where global passivity fails.
