If you definitely know the file is a Tinderbox document and are in a hurry:
- Open Tinderbox
- In Finder, drag the document's file icon onto the Tinderbox application icon in the Dock.
- The file should open
If this doesn't work, or when you have more time to fix things properly, follow this procedure to (re-)inform Finder how to handle files with a '.tbx' extension.
Read what to do if you get a "Tinderbox was unable to parse this file" message.