The point about Champollion is that, when he read the Rosetta Stone, he shared his results and communicated them in the context of a scholarly world, setting going a cascade of competence which created a viable Egyptological discipline. Clearly, from the absence of such a discipline, the Arab alchemists failed to do so.
To do something at a date subsequent to someone else is not to imitate them, or owe them anything, unless there is a clear chain of influence. I have never been convinced by the claim that because Gutenberg developed movable type a couple of centuries after a Korean king did, that therefore there is a chain of intellectual borrowing. Absent actual evidence of a chain, the picture is rather more of two people separately coming to the same elegant solution, partly because it is the elegant solution, rather than one of many possible technologies.
I am glad that there was an Arab alchemist who read hieroglyphics. Since no-one ever heard of him before, his existence does nothing to discredit Champollion's achievement.
The important thing is not just to discover something, but to communicate that discovery.
There is a down side to this - which is that to use the network of scholarly communication to communicate falsehoods is a particular sin. I've just been reading Bruce Henderson's True North which argues convincingly both that Peary did not reach the North Pole and that the discredited Frederick Cook did. Apart from the things Crook saw, and Peary did not, there is the fact that Peary and his upper-class allies used the media to discredit Cook, that Peary prevented Cook getting his evidence back home by threatening to maroon the trader with whom he had left it unless the man buried Cook's stuff, that Cook's companion on the climbing of Mt McKinley was bribed to withdraw his support for Cook's claims to have reached the summit, that a fake confession of fraud was inserted into an interview with Cook.
We should not think that the techniques of the Right Wing press were invented by Richard Mellon Scaife, just that he engineered their use on a far greater scale than ever before.
Honesty is mandatory for good practical reasons - it is important to acknowledge intellectual debts and to be punctilious about admitting the possibility of them, because the alternative is a free market of shouting claims.
The internet is a great mechanism for distributing both falsehood and truth and it is important that we opt for the latter.