Well, you come up with a language that is not Egyptian--there was plenty of it around, but nobody could read it yet, but you say it is not really Egyptian, it is a mix--it is "corrupted" Egyptian characters, but thought in Hebrew, which is also "corrupted"--Or----what it is, is slang, shorthand Hebrew, but written in slang, shorthand Egyptian which does not exist anywhere else but within this one society that has been wiped out and nothing but these plates exist. Then you have a stone that you put in a hat that can decipher this. Then the plates are again hidden from view. No one can say it isn't what they claim.
There is a precedence for this---after all God wrote the 10 commandments with His own finger, and you can't find them now to examine them, either----mind you, the God of the entire universe with no end of gold, diamonds, no end of precious costly materials at hand and that can create more out of nothing chooses stone to write on!!---However, some poor, never heard of "kingdom' that there is no record of anywhere, nor even mentioned by any other ancient peoples, write on gold! There must have been tons of it around and there should be a lot more still there---if not now, at least at the time the plates were found??? Perhaps even one really rich gold mine close by?? If I weren't old and decrepit I'd go hunting.
Now, if this were of a "demonic nature"--I would think Satan had enough brains to have some corroborating evidence around--pottery, tattered linen, a little sample of another gold plate with at least one letter of this alphabet--a piece of pottery from some other ancient people that mentioned this group--something that would make it more believable. He is pretty clever and this falls just a little short of his brilliant work, so I wouldn't call it one of his masteroieces-- But, who knows, maybe he'll correct the oversight yet.