Copy away, I lurk on that group also.
Actually, there may be a little hope...that nylon part is pressed onto the vent hinge ... it looks like there is still some material poking out, you make be able to press another A on and have it stay??? That's how its originally made, just pressing that part on...Of course you'll need to find the part.
Or get a little vice grip plier on it, tie a string on it, and have heat...
If not, then you seem screwed...you'd have to put in a new heater box, and that's not something I'd look forward to doing...of course I live in Florida, our nuts don't freeze down here until January...!!!