433 or 315Mhz RX to switch MOSFET via UNO [SOLVED w/ Thanks to PaulS]

A quick peak in the header file shows:

    unsigned long getReceivedValue();

So, you could have changed

    int value = mySwitch.getReceivedValue();

to

    unsigned long value = mySwitch.getReceivedValue();

and the code would have worked.