Hi, Garry. Thank you for your effort. I appreciate it.
I guess I will build a brand-new document. And this time and from now on I'll make copies along the way when working with Affinity.
None of the reasons you suggested are not possible.
The folder is right, I am the only person working on my only one, not connected computer, nothing else was running along clenaing-wise. And if I accidentally deleted the file it would be in the bin, right? But it was not. Nor anywhere else in my comp.
I learn every day, so any bug- or trick knowledge according to Affinity is precious to me, that this won't happen again.
Best,
Helena