Very interesting question. I’m impressed that you even realized that it was a sheilah. If I had been in that situation, I don’t think that I would even have realized there was a sheilah – I would have assumed that I could continue eating w/o a bracha.
Meno makes a good point, but I think the issue may also have to do with the way that we view rice, since rice is a safek to begin with and if you make an al himichya on rice, b’dieved you are yotzei. I want to look into this when I have a chance. Thanks for the “food for thought”.
Lowerourtuition: My impression was that he didn’t realize it was a sheilah/safeik until afterwards.