My Green card for 2year expired whch was valid till 2009 as i was married to a US citizen and was granted 2 years Green card. I got divorced in 2007.

I married a US citizen in 2006 and was granted a immingration visa and green card (conditional )in 2007 valid till 2009. However, my husband was not ready to start a married life and wanted tro concentrate on his studies, due to which without even letting anyone know he sent a piece of paper with a notary on it saying '' He is releasing me from the marriage''. He didnt file any legal divorce. Now that, my green card expired and i''m in Inidia. How can i travel back to US. I want to apply for legal divorce or apply back for my green card. what are the chances oif me getting a visa. what kind of visa i can apply for? My in-laws kept my green card and did not hand it over to me when i was in US, so i dont have GC but i have a welcome notice to USA, social security number. Does my social security number be valid till now? Thanks a ton in advance.