saved and stopped for the night, come back this morning, and the notebook is empty.
it was saved as Basics.ipynb. it appears to have auto saved an empty notebook over it.
edit; i’ve decided to just restart in jupyterlab on my computer, then just backup online every now and then.
still a problem, and i’d still like some sort of automated recover thing, for when the server just drops the notebook file, but oh well.