I already did
It's a confidential unit and they cannot give info to non-family. However by sweet-talking the nurse I more or less got her to "admit without admitting" that he was there. So "if he were here, he'd be in PICU." P must stand for protective, as in suicide watch. Now, this does not necessarily mean that he attempted such (for all I know he may have, but you can't conclude that from the limited information).
Anyway the card should go to PICU and MUST be deliberately worded without emotionalism. It is better if I am not the direct addresser.
