You also need to remember that the handbook covers ALL models in ALL European countries. There will also be some small print that says that specifications differ from country to country and not all will necessarily be fitted to your vehicle. Some are also options. Do not believe everything you read in the manual.
The tyre pressure sensors themselves are part of the trye valve, with a "receiver" unit mounted under the car somewhere which sends signals to the
There should be a "warning" light that shows a picture of a "tyre/wheel" that brifly comes on when you switch ignition on, this merely tests system ( same as air bag,
lights etc). On the higher spec lagunas you also get a display informing you of exact tyre pressures, not sure if Scenic had this feature.
As you have not seen this light come on, you either a) have not got pressure sensors, b) there is a fault or c) the pressure sensor sytem has been disabled.
The safest bet is to take the car to a dealer and check for you.