I was a semifinalist last year but ended up not getting the scholarship. From looking at a bunch of threads from past years, it appears that they notify semifinalists within two weeks of the submission date (last year I got my notification on June 7th; submission date was May 27th).. this is pretty consistent across all years. I would say that if you haven't heard within a few days, you may not have been selected as a semifinalist.
I was a little bit worried too. I have been a semi-finalist for two years and Tylenol usually notifies us within 1-2 wks. But, things just might be different this time. I'm optimistic...I know I worked hard. We all just have to keep our fingers crossed and pray.