It's happened to me twice now where if I resize the IDE by dragging the edges the IDE freezes with message "Resizing..." in the message area (no idea how to replicate the bug).
The first time I opened Task Manager, went to processes, and ended the QB64 Task. When I reopened the .bas I was not prompted to recover data, so I lost everything since my last save. No combination of ctrl+z'ing or opening other windows helped.
The second time I did a hard shutdown (hold the power button on your PC for 10 seconds). After rebooting and opening the .bas QB64 prompted me if I wanted to recover my data. The auto-save worked.
I couldn't find any info online, so just posting this in case it happens to someone else.