Unreal not saving correctly?

I’m hoping someone can help as i’m still a beginner.

I just saved my project and re-opened as I had to restart my PC, and it appears I’ve lost 5 hours of progress.

Windows Explorer tells me all folders (e.g. Config, Content, Intermediate etc. - including the several autosaved ‘.umaps’ listed) have been modified in the last 15 minutes however my project file has a last modified date of 5 hours ago. Additionally none of the assets I added since that time are present in the Content folder and neither are the data tables or structs.

From the Recovery folder, I’ve pasted the latest .umap, and ThirdPersonBP and StaterContent folder contents as that’s all there is (no .uasset file) and it loads a black screen with a few maps listed. Clicking on any but the last, duplicates them and the last opens and even older version of the file with a host of errors such as ‘failed to load Outer for resource ‘Arrow’’.

I don’t understand what’s happened, there was no crash report, I simply saved and closed the file. Any help would be great.