Summary:
If you steal toss on Rubick you cannot steal another spell after. If you would click your spell steal it says: "Ability not learned."

Repro Steps:
1) cast toss on Tiny
2) Rubick casts spell steal on Tiny
3) Rubick after spell steal cooldown expires cannot cast spell steal

Result:
It only says Ability not learned

Expected Result:
That you can cast spell steal after cooldown expires.

Extra info:
I had a Aghanims on Rubick, not sure whether it matters.
Match ID where I first encountered this bug: 3545636257