I've had this happen twice now. The first time I thought it was user error but now I'm not so sure. A sketch I haven't edited for a while is gone. The .ino is there, but it's empty. Anyone else run into this? It's not a huge deal to rewrite the code but it sure is frustrating.
There is an issue open for this problem in the main CREATE EDITOR section.
But you may want to also mention it is using the CHROME version.