Oh, I was embarassed all right. I had been practicing for 10 years at the time and hadn't "graded" for a number of reasons (changing dojos several times, for one) but the sensei I was asking about borrowing a belt was the shihan for Canadian Aikido Fed. He laughed and handed me the borrowed black belt and said something along the lines of "it's OK, wear it today" when I protested that I was only nikyu and shouldn't be wearing a black belt...
I'm assuming you're talking about Kawahara Sensei... he's a funny guy... he once gave me a yellow belt (even though we don't do coloured belts here), when I got my gokyu (that he just gave me without testing me). I was 11 or 12 at the time but I still felt weird being the only coloured belt around.