I've noticed that using my mains tester the light in the screwdriver lights up regardless of the position of the light switch near the door. It seems to only not light up when both switches are in some "off" position (although you can't see which is on/off).
I thought that the lamp is after the two switches so even if one of them is in "on" position and the other one in "off" the wire should be dead and only be hot if both are in the "on" position.
So... if this isn't the case at my appartment does this mean that the lamp is actually between these two switches so that when the first switch is in "on" position the wire at the lamp is hot?
(Actually yes, there's no such thing as on/off position. In usual multiway switching they just need to be both in the same position for the circuit to be closed.)