Ahri/Zil bug

So, was playing an aram, and was on very low HP, had Zil ulted me, and i ulted into the enemy team. I died, but with Zil's ult, i came back. I had only used one charge of my ult, but as soon as Zil's ult popped, it put mine on CD, so i couldn't use my last two charges. I thought I had a 10 second window, but it was literally zil ulted, i ulted, i died instantly, and lost my last two charges. Happened more than once.