This is the basis for a suitable circuit:
It has a rectifier, a comparator to decide if the voltage from the rectifier is high enough to mean it should switch, then a transistor to switch the relay on or off.
If you motor you have is low enough current you could use a higher current rated transistor to switch power to the motor directly - though that means it can only ever turn one way; it would need a spring to reset the lock.
Using the relay plus switches in the motor circuit to detect the ends of travel of the lock mechanism means it could reverse and lock again when the relay releases; that's a separate bit of circuitry from the remote switch itself.
Components are not critical, any small signal diodes for the input rectifier and there are hundreds of different opamps that would work in place of the 3140, just about any single-supply opamp that runs at whatever supply voltage you want to use.
I'd just build the rectifier part first, as far as R1 and see what voltage you get across C2.
Rx is just a direct connection - the circuit is intended to be able to take high voltages in to it, which you are not using.
The 5.6V zener is likely too high, which is why you need to find out what voltage you get from the rectifier when the phone rings. Then set the threshold voltage (that was 5.6) to somewhere between half and two thirds the voltage you measure. You may only need to use one or two signal diodes to give a low switching point.