A family of Microsoft word processing software products for creating web, email, and print documents.
Have you checked for the new file in the file directory?
Save As to pdf does not change the current file but creates a new file in the appropriate format.
Save As to txt does change the name of the current file to a .txt extension, but the full content is still there. If you close it and then reopen in Word you will be asked to convert. It will lose all non-text elements. Open in NotePad and you will see the plain text.
Yes, it is disconcerting to save as Plain Text and have the page on screen not change.