Sorry for being blunt but: absence of evidence is not evidence of absence (of original texts in Arabic about Alaaddin that predate Galland etc).
A lot of the original stories may be verbal oral and not necessarily written, another lot may be lost (burn libraries etc) and this all happened from 400 to 1000 years ago, so not exactly yesterday.
Indeed, this is why I say "no known original in Arabic."
But it is also possible that the Maronite storyteller was from a somewhat different storytelling tradition. Maronites are a Christian minority in the Levant which was traditionally involved in maritime trade, so they might have different sources for stories. In the end it is all guesswork since Gallard is the only known source of the story.
At one point a manuscript was found with Aladdin in Arabic, but it turned out to be an Arabic translation from Gallard!
A lot of the original stories may be verbal oral and not necessarily written, another lot may be lost (burn libraries etc) and this all happened from 400 to 1000 years ago, so not exactly yesterday.