Originally Posted by Missy

Yeah, if the cat has lived in the same house for a while, it will usually come back on it's own (unless your sister lives on a busy street, then it's high probability for it to become roadkill). It's not unusual for boy cats especially to be gone for a couple of days. But you should definitely have your sister call the shelters and pounds in the area because if it possibly was picked up and taken to a shelter, they only have to keep them for 3 days before they either put them up for adoption or euthanize them if there is no room in the shelter.

On another note, I lost my cat for 11 days and just got him back on Sunday. I posted an ad in the newspaper and posted signs around the neighborhood, and eventually somebody saw him about 6 blocks away and recognized him from a sign and called me. If your sister's cat doesn't come home within a couple of days, she should definitely start taking action.