After CA5 crashes, I am getting a pop-up window saying, "Unsaved project data found. Would you like to update your project with unsaved change?"
On answering, "Yes", all that happens is that I am taken to the last location that I used a file from, on this occasion a folder with images in. I have added this problem to Feedback Tracker

This is the same in CC4 and iC8.
When the program crashes and you open it again, you will receive a warning as you mentioned, and you must first save this lost file by giving it a name by pressing Yes.
Then your project should open.

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Aha! Makes sense. Will try that. Thanks.