GuitarScientist monitors if you lose internet connection and warns you when you are offline. If that happens your undo history will still be kept into your browser memory and you can keep working, you will be able to save all your work once you restore your internet connection. The browser memory gets cleaned once you save your document in your profile.
If your connection doesn't come back and you are forced to leave the editor without saving, the next time you come back the application will notice that you still have your document data in your browser memory (because you didn't save and so you didn't clean it), and will ask you if you want to discard and delete those data, or if you want to load them in the editor and start working from where you left.
This function also lets you recover your document if you leave the editor by mistake (for example you close the browser window without saving, or your computer shuts down because of a power outage).