That’s a pity. It does sound like your latest edits will be lost. Leaving a project loaded and idle without saving is a bit risky though.
I set Autosave to 5 mins and limit to 5 versions, but I am also still in the habit of Cntrl/s after most operations and I save incrementally, changing the filename 2/3 times daily. Then nightly whole-project backups to another drive. That might sound excessive, but I got badly caught out a few years ago, lost about six album projects worth of data due to a bad drive and the stress was enormous. Eventually using a specialist lab, I got the data back, though it cost me £750 to do so. I still think that the fee was well worthwhile.
In recent years Cubase has become a lot more stable and I don’t get many crashes, but when they very occasionally do happen, then .bak usually gets me out of trouble.