macmater, I'm not an expert but I can't resist chiming in here.

The KBX entry at Tatiana's TOMATObase discusses this issue. Apparently something less than 2-3% of KBXs revert to RL (proving that the issue of leaf type is much more complex than we usually think).

At this stage, you don't know if you have a stray seed (mixed in at the grower or packager's -- could be any RL), a KBX cross (with who-knows-what!) which occurred at the grower's, or an actual RL KBX.

You'd need to grow out your plant and compare everything to a normal KBX to see if you have an actual RL KBX or something else.

In any case, the chance that your RL plant is a Kellogg's Breakfast is almost nil (only if a stray Kellogg's Breakfast seed somehow made its way into your packet). Leaf type is not the only difference between the two varieties.

KBX at Tatiana's

I had the same thing happen to me when i planted KBX a few weeks back. I am pretty certain I did not have any stray seeds. I was wondering the same thing as you too. So I am growing it out and going to compare.