Period sex NOT messy?

Fay • I`m a Scorpio. <3 I love knowledge, sex and everything that comes in between.
I had sex recently while on my period. Totally UNPLANNED and a sneaky attack while I was napping. Anyway, I was super duper heavy that night. Like after I went home I KO'd and bled EVERYWHERE. D: Regardless, during sex blood DID NOT get everywhere and it WASN'T a damn Dexter murder scene as I had expected. I was surprised, and relieved because I was embarrassed.
​So my question is, how is that possible? No condom. No towel. Nothing. Only thing wet that came out of me was my body's natural lubricant, and a little pink.