[GAMEPLAY] Rammus e goes one cd despite not tauting enemy

Couple of times in the game when i used my e with rammus just before enemy run out of vison it went on cooldown despite it din not taunt an enemy. When i alt-pressed taunt icon to show my teammates i really used my taunt it showed "its ready", meanwhile icon showed its on cooldown. I was unable to reach enemies afterwards to check if it was really on cooldown or it was just just visual bug. Have no friends to recreate that bug Kappa. Happened like 2 or 3 times.