Eww... that's not what I think it is

Right?! That's not... that hardened mass in the carpet fibers... that's not... the previous owner had cats and... surely not... I had to pay a $300 non-refundable cleaning fee... The manager himself cleaned it, or so he says... and surely... surely...I sent the picture to the apartment manager. Two-thirds of my carpet has since been replaced.Carpet is the worst.