Correct SEO for Yahoo and strange Yahoo Search indexing behavior

Hi, fellow SEO fellows. I have a budding website, only weeks old and not full-fledged yet, where I am beginning to promote my SEO business and write up my random profound thoughts on such stellar subjects as Correct SEO, SEO Secrets, Benefits of Search Optimization and whatnot. I would appreciate your clicking around and letting me know any thoughts, but my question is about how the site is indexed in Yahoo.

Like many SEOs, I use my site to experiment -- do this and that and see what happens re. rankings and such. I got fully indexed on Google within a week of putting up the first version of this (admittedly new and small) site and was never stuck into the Google sandbox, so now I actually have a few rankings on Google. But Yahoo is a different story. Some days later I noticed that I had also been indexed by Yahoo -- at least my home page was among the top results if you searched for my domain name (Search Benefit, but without the space). I was glad to see that Yahoo had indexed me, and I forgot all about it. However, a few days ago I checked the Yahoo website analyzer again and noticed that my site had been dropped from the Yahoo index. The backlinks were showing up all right in the Website Analyzer, but NO pages. My SEO heart bled. I had not engaged any despicable SEO practices such as keyword stuffing or (horror of SEO horrors!) link spam, yet the site was gone from the Yahoo index. (For the sace of completeness, I had submitted the site to the Yahoo *local* directory, and seem to have been denied -- I am not sure whether this has any SEO relevance, but I thought I'd mention it for the sake of completeness).

Anyway, today I checked again. Ah the dream of comprehensive, bulletproof, correct SEO multiplied by the restlessness of the Search Engine Optimist! And strangely, I see that today the Yahoo index contains a single page from my Website. The SEO mystery continues because the only indexed page is not any of the normal content pages, but actually my XML sitemap (/sitemap.xml). I have to admit that I have NEVER seen an xml sitemap showing up in the search results of any search engine ever at all. Have you?

So my question is, can anyone explain this behavior? What are the "SEO secrets" for ranking well in Yahoo? Any tips on how do correct SEO specifically for Yahoo? All this has got me thinking. I all my years in SEO I have focused almost exclusively on Google, but what seemed to be a good practice for Google also seemed to work fine on Yahoo, and apart from that I never gave it much though, perhaps a serious SEO omission. Seeing this indexing behavior, which is a first for me, suddenly makes me much more interested in Yahoo.

Any thoughts on this from the Yahoo gurus and other SEO practitioners? Please share!