Sylas and the r disappearance

Basically, whenever you steal an ult and try to use it while you cannot like I don't know urgot's r you throw it, the target gets it and press r again before he's below the 25%... well there goes the ult, it just disappear into thin air and you lose it, cancelling the urgot r. Happens every single damn time, took Garen's ult, ulted him but he died before even starting to cast, it's gone. Best instance, Neeko's ult... Start it and flash at the same time to get to the ennemy... the ult never showed up and I lost it, made me look like a fool and die. I get that it's one time and you should lose it if it's a channel let say and you get stunned, but losing it for no reason is quite annoying. I don't know if this is intended or if people get it a lot... I'd like to know because it makes me lost quite a lot of ults for no reason.