If the capacitor is initially charged with Q charge and then conected to a inuctor then discharging takes place and the energy stored in electric field gets converted into the energy stored in magnetic field. Energy of a LC oscillator oscillates in the electric field of capcitor and magnetic field of inductor and the energy remains unchanged for ideal case.
Now if we placed a coil near the inductor then with the changing of current magnetic flux associated with the coil also changes and that causes an EMF in the coil and if there is resistance of R with the coil then there is some loss of energy but the energy in LC oscillator remains unchanged.
Where from the energy comes that is lost in the coil?