I'm sorry that you lost your save, and it is one of the problems with my current save system.
I will add a export save feature once I get around to reworking the save system. This will sadly not be for a while :(
I do not have that option activated, as all other games that also use the local storage still hold my save...
Another thing I found out is, that when I duplicate the tab it gives me a fresh save. But if I first made a manual save it sometimes gives me the same as the save of the other tab....
But okay thanks for working on a save system with export/import ;)