Never, since it was never lost. We Jews have had it, learned it, cherished it and obeyed it since it was given by God 3300 years ago.
Firstly, the academic claim concerning Josiah refers only to Deuteronomy. There are secular scholars who theorize that a book which was found in Josiah's time (2 Kings ch.22) was Deuteronomy and that it became part of Judaism and the Torah at that time. This and similar theories (such as Joshua, Judges etc being composed in that late era), are not backed up by any physical evidence.
The fact that Josiah "made reforms" is misinterpreted by some, as meaning that he started something new in Judaism. That is not the case. Rather, he simply swept away the incursions that idolatrous misbehavior had made (2 Chronicles 34:3-7) into part of the populace, exactly as Samuel had done (1 Samuel 7:3-4), as well as Asa (2 Chronicles 15:8), Jehoshaphat (2 Chronicles 17:6), and Hezekiah (2 Kings 18:4).
Moses did not have a "stepfather-in-law" since his wife, Zipporah, never had a stepfather. Moses' father-in-law was Jethro.
No they were not given to Moses.
Robert Boyle in 1662; rediscovered in 1676 by Edme Mariotte.
Jethro, Moses' father-in-law, was affiliated with the religion of Midianism.
Generally attributed to Moses. It was Jehovah who gave it.
Moses was in Egypt, his wife and children might have been there or with Moses' father in law.
The Law of Moses was given as a preparation for the coming of Messiah, which we know now is Jesus Christ. The Law was given to show their sin and their need of a Savior.
it is not known who rediscovered the Corpus Juris Civilis, also dubbed as Justinian Code. It is known that it was rediscovered in a library in Pisa in 1070.
his brother in law.
Moses
The Ark
5 books of the law of moses