Um...each developer will have a working copy on their local machine. This is most likely to be the last known good version. A quick diff will show up the changes that they've recently made and they can verify that the differences are valid. It's really not that complicated.
If someone wants to go through the trouble of hacking the version control to the point it can propagate to the developers machine, stop them from reverting changes that may have been pulled down just before the repositories were locked down, I'm pretty sure they'd be smart enough to break into sourceforge without making such a big mess and alerting everyone. We can go around with increasingly unlikely scenarios forever but the fact is, a quick check is all that's realistically required.