A memento from a good blowjob. A blowmento is when you're taking a piss the day after getting a full service BJ and you find one of the girl's extra long hairs stuck somewhere in your package.
Guy 1: Dude, check it out. I found this blowmento wrapped around my wiener while I was taking a piss.
Guy 2: What's a blowmento? That's a piece of woman hair.
Guy 1: It's a hair from that broad I met at the bar last night, it got stuck in my junk while she was blowing me last night.
Guy 2: Get out of my house.
When something that should have documentation in one document is instead documented over blog posts that are incomplete or hard to find and often spread over different blogs.