The other one was probably parked up close to the star so you didn't see them. They then targetted the low intensity wake left behind when you drop into regular space and homed in on that.
Hi tricky.... no - it was well away from the star, and on my way to the station. So - you leave a low-intensity wake: is that actually a signal? I thought you leave one when you enter supercruise from normal space, but not vice-versa?
Any clarification would be really useful!