The software required configuration in order to keep backups of the items added to its database. Backups can be configured through the View > Options > Backup. If the No backups option was checked, then you won't see any backups in the default folder where Whisper32 kept them (by default backups where stored in the default installation directory).
Here is an image with the Backups settings window that you had to access prior to this issue:
![enter image description here](http://image.prntscr.com/image/e90099f2db5548d6b4d37a7e34ecff8b.png)