Google strangeness

Where did my home page go?

[wrgvt]

Something very strange happened last weekend. The home page for one of my sites disappeared from the Google SERPs. It used to be #21 for my most popular keyword and #1 for the second most popular. My site has about 800 pages below my main page, and they all appear in their normal position in the SERPs.

What's strange is that my traffic doesn't appear to be affected and I'm still seeing referrals from www.google.com/search in my logs.

I must say I'm confused. I was aghast when I suddenly couldn't find my home page in the SERPs, but after 4 or 5 days, I can't see that it's had that much effect. So how can I still be getting traffic to it from Google?