That star system is young, and the planets are therefore hot enough to produce their own infrared light. That light is what the telescope saw. So, there was no

That star system is young, and the planets are therefore hot enough to produce their own infrared light. That light is what the telescope saw. So, there was no need for the planets to pass in front of the star to be detected. In fact, if you click on the picture in the article, you see two planets and the star quite a distance from each other. Those planets are much further from their star than any of the (known) planets in our own solar system.