This has happened before....almost identical to this  It is likely, imo, that USCIS will find that letter and revoke the I-129f.  In the case I remember, the I-485 was denied. They might want to withdraw the I-485, and immediately file a concurrent I-130 and another I-485.  Just my opinion.
 
	They will likely have a lot of explaining to do.  Legal representation is probably a good idea.