I lost that session of around 2000 tabs back in May 1, and I backed it all up onto a folder. When I followed all the existing steps (closing Firefox and replacing the current stuff with the backups), it only took me to a blank "about:restore" tab and popped up an about:support tab. When I tried loading it into the scrounger (https://www.jeffersonscher.com/ffu/scrounger.html), it crashed the tab no matter how many times I try. I decompressed it and it loaded the uncompressed JSON without a problem, but it won't let me click "save embedded session (first found only)"