I also had this exact same issue, Same version as well.
I had autosave enables for every 1 minute, along with my own normal frequent saving. ( The autosave did pop up every time in the lower left hand corner) Got everything rigged (saved it), Switched to Streamer mode, set it up in OBS. Then next time I turned on my PC the saved pngremix file was empty, there were 0 autosave files, and OBS was still setup from how I had it.
Nothing was in the recycle bin either. Not sure what happened, but that was about 5 hours of work I lost.