The input to the "amplifier" is the emitter impedance of the transistor. I can't remember the formula, buts something like Hfe/Ic(in mA), anyway its low, say 25 ohms. So the voltage across R6, sends some current down through R6 to earth and some into the emitter (the importent bit!). Because of the action of the transistor this current (or at least 99% of it), flows through the tuned circuit, causing a voltage to appear across it, there is also the output resistance of the transistor shunting the tuned circuit (high resistance 20K?). Its is this voltage that sends the current through C5 into the emitter and causes the volt drop across R6.
Frank