I have to agree with Victor, I've never seen nor heard of that happening. I don't qualify myself as anything close to an expert on this, but I have had non fixed females and never seen any such thing. I would think something else happened, and maybe they just assumed the cat was having a period? Without getting graphic and keeping this family friendly, males have certain attributes on certain parts of their anatomy, that induce ovulation during mating, and with a healthy female, that should be the only time they ovulate. I'm sure there must be other things that could stimulate this, and possibly induce ovulation in a female, but as far as I know, that is extremely uncommon.