Do you notice when you are spotted in the Matrix ?
No.
(but you will notice the follow up data spike)
is that RAW ? with modern day explanations you notice someone "pinged" you, you know you are spotted.
When a player character does not notice someone spotted him the player has to act as if he does not know he was spotted. (Note: some GM dont like rolling hidden, i am one of them)
And many players i ve met are not properly able to do that (act as if nothing happened).
Rigger in your example will also gain a tactical advantage when being attacked by the decker (it is actually not very likely that the decker will land any damage at all).
The hacker has all the time in the world to wear the Rigger down. And i dont think that it will be fun to play that fight out. And when you use an equal Prime Runner instead of one of the worst Mooks in the Book its not that easy anymore, for example lets look at the Decker Archetype p.84
He has Attack rating 9
Cracking (Cybercombat) 7+2
Overclock +2 (1 Wild dice)
Logic 6
Thats 17 Dice (one of them Wild) and DV5
The Technomancer Archetype has no Cracking, since thats no default skill he cant use his Attack 8 for DataSpikes...

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But so long as the RAW stands and you can combine Cyberdecks with RCCs it's actually quite viable, if the Rigger is willing to make that investment.
That was one of the reasons i actually made that thread for. A Rigger without a Hacker seems very vulnerable. If you want to make it happen, it can be done. But not in a classic Runner setting imo. For example a Hunter that hunts Paracritters, there the Drones shine, no hackers, many magic abilties dont help against drones ...
edit:
just noticed that the Cyberjack VI is correct listed, so changed the post.