The age of your MBP should have no bearing on the App store account. For reasons that are not clear to me, the older OSX's that have been installed on your MBP are not to be found.
To get back into operation, you can purchase the Snow leopard disk and install 10.6.3 in your MBP:
http://www.apple.com/shop/product/MC573Z/A/mac-os-x-106-snow-leopard
Then run the Snow Leopard combo update that will install 10,6,8:
https://support.apple.com/kb/DL1399?locale=en_US
That will allow you to install any of the newer OSX's. However since none of them appear in your in your App store account, you are limited to Lion, Mt. Lion or El Capitan (Mavericks and Yosemite are no longer available). Lion and Mt. Lion are available for purchase from the Apple online store. El Capitan is free, but that is not what you want.
Ciao.