Well, sometimes steaks don't get cooked quite enough.

I had a guy working for me who was all fired up about the superiority of Buffalo over cows. He found a place selling Buffalo steaks and went out and got a couple (along with talking about how superior it was, which we had all heard before). When he didn't show up at a meeting the next day, I knew something was up, so I called him in the afternoon. He told me that the farthest he had made it from bed all day was the toilet.

It's a bit rare, but if the steak is equally rare...you might get a little extra. Nothing else in your meal sounds like a likely source, except that I have recently heard from a friend that he was pretty sure he got something from ground pepper.