could of just been a stray cat, did you look for it at all?
mind you, animals can be spirits. i had a cat who died, and for years i could sense him. when he was alive every night at 1 he'd come into my room, jump onto my bed and curl up at the foot of it. after his death, at 1 i could hear my cat walk into my room [he always purred really loud, and my other cat never purred] then i would feel something jump onto my bed and walk back to that spot and lie down. sometimes when i moved my legs i felt like something was stopping them. i'd turn on the lights the first couple nights this happened, and there was nothing there, but there was an indent that looked like my cat was lying down [or had been] same thing happened with my dog some times, i could feel him beside me.
so yes, it is possible for you to of see an apparition of a cats spirit, but it's more likely it snuck in. it's a garage, and with people coming and going at a party, and it starting to get cold outside, i could of snuck in when the door was open or there could be a hole somewhere. if this continues, like you keep bumping into a random black cat that vanishes, could be a spirit that's attached to you, but you'd need more occurrences before we could draw that conclusion.