Stealth Check and Psi-Bolstered Knack

Hi all.
I've got a Soulknife Rogue player in my campaign...

Psi-Bolstered Knack trigger on a failure check.
Failing a stealth check means someone saw you.

---

Usually when someone wants to stealth, I make them do the stealth check and write down the result.
Then, later, I roll the active/passive perception of possible npc/guards.

Problem: if a stealthed creature manage to detect my stealthed player, it means the player failed the Stealth Check, and in that moment he could add the Psi-Bolstered Knack die, but for this to happens I have to warn the player "someone saw you" , revealing there was someone else hidden.

---

The other method is to have the rogue be stealthed, but make the roll check only when someone else is about to make a perception check (or passive), but this have the same problem: I have to inform the player about the existence of other creature (which possibly are stealthed and might not reveal themselves even after detecting the player).

---

Ideas?