We've gotten to park near Janet & Gary and their Minuet at a couple of rallies, but other than that I don't think we've seen another Argosy in the same campground. We have driven by a few, parked in a long term campground or in someone's yard. But, as mentioned previously, there just don't seem to be many of them driving around.
We do, however, park next to an Airstream on almost every camping trip. Our friends bought a 1979 Ambassador last year and are loving it!
But, after your story we have high hopes to meet another Argosy (or two, or three!) out there somewhere. Happy Camping!