Rek'Sai burrow prob , when i am burrowed and i catch up to foot steps i cant see person !!!

when playing her i burrow to move, when i see foot steps i go after but most times when i get to the foot prints or next to them i cant see the champ making them... all i still see are the tremor sense foot prints .....i thought u where to see them when they are in saame space or really close to u....