I tend to have this same problem from time to time. Here is what is going on, in my best judgement.
I use the following code to get the latest version:
wget http://downloads.sourceforge.net/project/moodle/Moodle/stable33/moodle-latest-33.tgz
For example, yesterday I was planning to start my upgrade (on my experimental moodle) and I issued this code. However, just as what happened to you, I did not get the latest version. For whatever reason, sometimes the latest copy of moodle, as shown on the moodle.org webpage (where Howard directed you) does not immediately make it into the sourceforge system. It seems to eventually make it there, but can take a little while.
When I download moodle from souceforge and check the version.php information, and see that it is not the latest moodle, I simply download the latest moodle from moodle.org and FTP it to my server in order to continue with my upgrades. The copy of the latest moodle on moodle.org is always accurate.