If you launch Rust via a shortcut you’re probably going to be pretty confused next time you launch it because you will find yourself in Experimental. If you want to play the previous version that hasn’t been updated for 6 months (now known as ‘legacy’) you can do so by launching via Steam..
If you’re resistant to change and don’t want any part of the new version you can switch to the legacy branch. This way your shortcut should start working again.
You can read more about how we’re developing Rust here. If you’re an experimental newb you’re in luck – Rustafied has put up a bunch of pretty good guides to help you adapt.