Yes, I've had that happen, it's how they discovered that I have crohn's. Only they found a bleeding
ulcer in my TI area, and they were able to stop the bleeding. I remember feeling lousey for about
a week before the massive bleeding hit too. My blood was also a bright red, it was coming out so fast it never had a chance to turn dark. I don't go by color anymore, I look at how much blood there is.
I wonder if your bleeding site was in your small intestine where the scopes couldn't see. And I agree that hemmies probably wouldn't bleed out that much, and probably would be quite easy to diagnose for them. I don't think many realize that we can really bleed out with Crohn's, and it's something to be aware of.