Sometimes an artist cannot recover its own files.

This may be due to a method that is not sufficiently deterministic to distinguish the running Aseprite instance from a previously launched Aseprite instance using the process ID (PID).
It turns out that the probability that the PID of a closed Aseprite instance matches the PID number of a subsequent Aseprite run is not zero, nor even low enough to leave it as is.

Report with a workaround: https://igarastudio.zendesk.com/agent/tickets/7783
When you go to the Home tab > Recover Files > Refresh and nothing appears, it's recommended to:

1. Back up the desired session folder.
2. Go to the desired session folder.
3. Change the number in the pid file and save it.
4. Go to the Home tab > Recover Files > Refresh

Aseprite version 1.3.14.2