ARAM bug with Oracle's Extract

Unfortunately I do not have video evidence, nor am I 100% sure this is correct. I just played an ARAM as Zilean and bought Oracle's Extract in order to see Teemo shrooms. While Oracle's was active, I died and resurrected with my ultimate. I was still able to see Teemo shrooms for the rest of the game without purchasing Oracle's again. After I rez'd I could not see the outline of Oracle's though, just had the true vision effect.