Google XML Site Map Plugin Virtual Robot Txt Problem?

I noticed yesterday – yahoo and bing are not showing my home page when i query my website name rather it is only showing my /about-2 page as the top result. I am not sure if the following scenario is the reason and I want to see if anyone can shed any light on this? I was using a contact form plug in that shall remain nameless, but it created a 16+ indexed pages (in google) on my site that weren’t necessary (it has done so for the hundreds of thousands of people using this too just not sure if they are aware yet). I contacted the developer and he suggested I add a robot txt file to stop those pages from being indexed. I did, not knowing that the Google XML Sitemap PlugIn also has an option to include a site map url to wordpress’s virtual robot txt file which is the robot txt my site had been using and working fine. however the xml sitemap option ONLY works if you don’t have a “real” robot txt per the fine print under the check box on the xml sitemap plug in. so in creating the robot txt file in my web root directory to stop the 16+ pages from indexed it took away the robot txt for search engines to find my sitemap. this said, i am wondering if the robot txt file i added in anyway could have caused my homepage to stop showing in search results in bing and yahoo? prior to this i was ranking for key words in yahoo, pretty well, google indexed most of my site pages, and urls on the sitemap, and bing was catching up. all listed my homepage when querying. i since have deactivated the contact form plug in, deleted from my root directory the robot txt file the contact form plug in developer suggested, and added google xml sitemaps viritual robot txt file back in. webmaster has downloaded my site map robot txt file again so that seems to be ok, but my concern is that yahoo and bing are NOT showing my homepage in search results. anyone have any idea if what i just suggested could have caused my homepage only to drop out of search results? and if not what could have happened?