It’s easy to do. You’ve most likely created a new FastCapture file rather than reopening your existing file.
Close the FastCapture3 window you currently have open, and choose New from the File menu. When the startup window opens, locate the original version of the file you were working on in the list to the right or by searching for the file on your computer.
If you’re continuing to work on a file, it’s always best to open it from the list of recent documents in the startup window.
Helpful Tip: By default, FastCapture saves files to your Documents folder. You can always continue working on a closed file by double clicking on it from your Finder.