Filemaker does not automatically back itself up. It is thus a very good idea to save copies of your current project frequently.
What type of changes disappeared on you? New data entered in fields/records or design changes to the file?
If design changes are missing, you may be opening an older copy of your database as filemaker saves design changes automatically.
If your data is missing, you need to investigate and determine what is causing that as you may have a script or other design feature that is deleting data you don't want to have deleted.
Your database is stored where? Your database is shared how? You changes are made how?
These are the key questions.
I'm using the filemaker pro 11 advanced on a windows platform. The application is store on C: drive, with development on a subdirectory on C: drive. The platform is not shared, sole user application. All changes are made within the FP11A program including data entry.
Additionally, I'd love to know the naming syntax and possible location for the back up application, and I'm less concerned about finding the data.
There is no back up application.
To repeat: are you missing data or design changes you made to the database itself?