Matrix Perception isn't opposed unless the target is running silent so 5 hits is a hard but not impossible threshold.
Modifiers, +2 from VR, +2 from being a Technomancer, +2 from appropriate Specialization in Computer Skill, anything that buffs Intuition, Perceptive Quality (up to +3), Sprite power Navi from Kill code I think also buffs Matrix Perception but I can't recall, and the Primed Charge Complex Form will boost the next Matrix test which certainly includes a Matrix Perception test, and of course Edge.
And it's an NPC. You need 5 hits on 3 dice for Story reasons? Done, and carry on.
Also keep in mind, there are people who know if someone is a Technomancer, maybe your NPC knows those people. Or knows the Technomancer. Many, many ways to explain an NPC knowing something. Most of the time a GM doesn't have to give a backstory to the backstory.