AM demodulation circuit
The demodulation is done inside the chip - the chip produces the output lines that control the motor and this is the general clue about where AM demodulation is done.

Bear also in mind that the likely type of modulation is OOK (on-off keying) and this makes demodulation a lot easier because you are detecting the presence or non-presence of the carrier. Counting the number of modulated pulses that the transmitter emits is the likely method of decoding data from the transmitter.