Your motion sensing light has a wide field of view because of the lens you can see covering the sensor. Infrared energy is a form of light, so you can focus and bend it with plastic lenses. But it is not like there is a 2-D array of sensors in there. That is because glass is not very transparent to infrared energy. This, by the way, is the basis of a greenhouse.
Light passes through the glass into the greenhouse and heats things up inside the greenhouse.
The glass is then opaque to the infrared energy these heated things are emitting, so the heat is trapped inside the greenhouse. It makes sense that a motion detector sensitive to infrared energy cannot see through glass windows.