The source node in most cases contains the sample message as written by the developer. If it looks like a dot-delimitted string such as "form.label.firstname", then the developer has not provided a default message.

Could not find Form Field with ID: '%identifier%' Nie znaleziono formularza dla '%identifier%' key: Could not find Form Field with ID: '%identifier%' Could not find Form for '%identifier%' Nie znaleziono formularza dla '%identifier%' key: Could not find Form for '%identifier%'