I think you're underestimating the impact of the Arnold sighting. Remember, Arnold didn't actually see saucers - but he was misreported as having seen saucers. Then suddenly people were seeing saucers all over the shop. Why? If Arnold's 'boomerangs' were the real thing, why weren't people seeing boomerangs? Where did all the boomerangs go? On the other hand, if you're going to rule the Arnold sighting out of the equation, then you still have to explain why fleets of flying saucers should choose to visit us the very moment after the press accidentally invented the phrase "flying saucer".
How Arnold's enigmatic observation of unidentifiable objects
gave rise to 'flying saucers' is a fascinating story.
Although I researched this in great detail a few years ago, I
didn't then have time to reveal all of my findings; I might
now be able to in the near future.
A 'flying saucers' depiction essentially originated because
the inaugural 25 June, 1947 'Associated Press' newswire, from
Pendleton, misconstrued Arnold's bizarre simile of how the
objects flew, "like a saucer would it you skipped it across
the water".
Local reporter Bill Baguette has been cited as first using the
phrase 'flying saucers', a claim which in later years he
refuted and indeed the newswire only described, "saucer-like
objects".
It may not even have been Baguette who wrote the newswire, my
research identified another equally likely candidate; Nolan
Skiff, editor from the 'East Oregonian'. The full story and
supporting documentary evidence are more complex.
I also unearthed a copy of what I discovered to perhaps be the
seminal media use of the inevitable terminology 'flying
saucers'.
_Quoting that same AP newswire_, the newspaper's own headline
evolves Arnold's 'saucer-like objects' to become "Flying
Saucers".
I had obtained the editor's permission to publish their
historical document and again, might now have time to revisit
this.
Pivotal is that subsequent to Arnold's story reaching the
media, masses of people then reported seeing 'flying saucers',
or 'flying disks'.
There were related front page news items for days afterwards,
amidst media hysteria which incorporated fears the Russians
had a new secret weapon.
By the time of his 1950 self-published booklet, 'The Flying
Saucer as I saw It', Arnold was an avid Fortean, quotes
Charles Fort therein and also highlights numerous Fortean
related newspaper articles.
Whether he was similarly inclined beforehand would certainly
be interesting to know.
Arnold confirmed that the object depicted on the cover of his
1952 book, 'The Coming of the Saucers' was essentially what he
recalled seeing:
http://i122.photobucket.com/albums/o240 ... ETCH_4.jpg
One affirmation is a 1977 local newspaper interview with
Arnold, reporting that his wife, Doris, "was wearing a
necklace with a miniature of the crescent-shaped saucer. The
necklace was made in 1948, a year after Arnold's sighting".
Substantially lesser known is a sketch which I presume to be
Arnold's:
http://i122.photobucket.com/albums/o240 ... ETCH_0.jpg
This was something of a Fortean discovery and featured in a
German produced video, 'The UFO Phenomenon' [or similar
title], I merely bought out of curiosity from a second-hand
video/DVD shop in a small Scottish town.
The image is shown as background to an evident radio interview
with Arnold, seemingly some years later.
Although the sketch and details of that broadcast were alerted
to UFO historians, the origins of both remained unidentified
[still to my knowledge] and I've never seen the drawing
elsewhere.
One significant reason for surmising this was sketched by
Arnold is that he included a similar outline - amongst others
showing a sequence depicting how the objects appeared to alter
shape - in a 'rediscovered' illustration, featured on the
March/April 1995 cover of 'International UFO Reporter'.
Bottom line; although pictorial representations of 'flying
saucers' had an antecedent, Arnold's misapprehended account
became the fundamental genesis of 'flying saucers'. As you
indicate, all that consequently became interrelated could
hardly have a more specious foundation.
As foremost 'ETH' proponent, Brad Sparks, conceded during
public correspondence:
"I am nevertheless bothered by the fact that no one else
in the 1947 flap ever saw objects shaped like Arnold's,
with only one possible exception (a suspected hoax
apparently)".