Graves Ult cooldown bug

During a game i was playing as graves i had used my ultimate as i died still doing all the damage that it was meant to do but when i was dead it said i had not used my ultimate removing the cool down completely. I have not seen this bug in anyway since i had first encountered it but i thought that if others have encountered it it could be a problem in the game especially in early game fights when the death timers are short.