The Islamic prophet's foreknowledge of the Terfeziaceae's health benefits

[Astreja]

Still, there is no report of using truffles' water for medicinal purposes before Muhammad. If such a knowledge was common before him, there would be accounts of it.

Not necessarily. It could have been common knowledge in the past (and not written down because it didn't need to be written down), it could have been transmitted via oral tradition from one healer to another, or it could have been written in a document that no longer exists (e.g. not written on a durable medium such as clay, stone or brass, or lost in the fire at the Great Library of Alexandria.) I don't think anything supernatural is going on here; I think that any knowledge that Muhammad may have had of the truffles' healing properties was acquired from other people.