I started XnViewMP, not realising that I already had an XnView-window open ...and got some error about the catalogue, that I ignored, as I assumed that it was just that it couldn't open it, in the second instance, as has happened before.
After I closed the second window, and checked stuff in the catalogue, in the initial window, and then closed that too, I (a little later) opened XnView again
...and saw that the catalog had been completely wiped.
Nothing remained.
Luckily, this was on my secondary computer.
(I edit the catalogue, on my primary, and then occasionally copy it over to the secondary. Due to the base path, most, but not all, category-settings on the primary, is properly reflected on the secondary)
...but if it had happened on my primary...
