Getting Closer.  I opened the QBO file in Text Edit and changed that number - saved the QBO file and then tried to import it again [I had already deleted the earlier missing transaction] -- the 4 that made it in before were not imported, of course, but the missing one WAS - I then just did the import as usual.  

So the issue is the # in the FITID line apparently has appeared before?  I did a search for that old # of the transaction - 526334 - no QBO files but some sort of article on vegetables!