The "rules" provide guidance for what iisn't a "no bird". Look starting on page 35 "Unusual circumstances, No Birds". Collapsing it down to a single sentence would yield something like "If the concept of the test is changed or the bird is not retrievable, it is a no bird." The rules section goes over several instances trying to point out that either judge can call it (doesn't take both) or what to do if you have one. However, there isn't any black letter law on what constitutes a "no bird".
If you felt that the bird was retrieveable and was not substantially different from others, let it go. The rules are very clear about each dog not needing to see the same test. What they do say is that the test each dog sees must be within the standard. Thus, distance may not make any difference if the cover is the same and the dog was able to see it, etc.
From your description in letters and characters, I'd say you made a good call.
Not so much in Jr but in Sr and Mstr, my co-jodge and I discuss no birds before the test, even to the extent of instances of what will and won't be a no bird.