Spellbook bug [Spell's icon doesnt update after using spellbook rune]

Was playing against a Nasus last game that had spellbook. He started with TP and Flash and after a few minutes he uses ghost from nowhere. I tought he changed spells with his spellbook but when i used tab to see what he changed it for he still had TP and flash. The icon's didnt update. I didn't knew he had ghost until the time he used it. Even on the post game screen he still had tp and flash. Is it a bug or something it's meant to be?