I was bit by this in a cordova app on a past update. After that I backed up api keys, etc to native storage using a cordova plugin and added a wrapper that will fall back to it if localstorage lookups fail.

I would advise others to do the something similar since unless you are packaging the browser too (like crosswalk did), then that piece is really out of your control and you shouldn't expect it to be retained.

A similar issue can be seen on iOS under low storage conditions where the operating system will clear the browser cache to reclaim space.