My site lists high for many keywords on google. I recently decided to create and submit a Google sitemap for my website in the hopes it would improve things "making their job easier". Well for some of the key terms I was on page 1 and now I'm gone. Only on some terms, but they were high traffic and relevant keywords. I am still on page one in the other data centers but NOT on www. Thank God it is only for SOME but all I DID DIFFERENTLY WAS SUBMIT A GOOGLE SITEMAP! I should have left well enough alone. I have logged into G and deleted the site map from my account. I hope this will not make things worse
Has anyone else had this problem?

You could be mixing up cause and effect. There could be many reasons why pages disappear temporarily.

Google sitemaps work perfect for me. Getting more hits per day