It may be possible to identify an infrared source orbiting a star by tracking the total infrared output as the source passes in front of and behind the star. It's the same basic theory as detecting a planet by the change in the brightness of a star caused by a planet in transit.

But the visible light transit is a very abrupt drop which may be easy to isolate. An infrared source would add to the total output of the star through most of its orbit except when it was actually behind the star. A very long curve with a short "negative spike" in it. Might be a lot harder to detect. I don't know.