Keynote loses file

While editing a presentation, Keynote crashed. The edited file has been completely lost and could not be found after booting Keynote and the system. However, the recent items list of both Keynote and MACOS displayed this item. But selecting it did not lead to any response.

The item has been retrieved from Time Machine where it was in the folder where it should be. This folder is on the same drive as Keynote and the system. Shortly before Keynote crashed, either the system or Keynote displayed a message telling that the location for saving the presentation could not be found. Thus, I selected the folder manually and saved the file. Around 10 minutes later, the crash came and the file was lost. It is not on another drive or somewhere in the network.

Any idea about this disaster?

Thanks for helping!