Mainly due to lack of cloud save - sorry about that :) Full version will have that so this won't be an issue then :)
But how? I literally closed the tab briefly by accident before I remembered to spend gold I had before bed.
Not 100% sure :/ As a temporary thing you can copy your save file from time to time and if this happens then just load it back in. In discord someone might be able to give you a save file that's around the progress you were at ;)
