Say what Iosias??!!! Just because it doesn't mention Sinai in Deut doesn't mean a thing. Exodus does.
Von Rad's essay was pioneering and is well worth a read. My point was that the narrative of the Pentateuch is build up from a variety of sources. These sources stem from cultic activities where a confession of faith was said. Deuteronomy is one of the earliest, if not the earliest, confessions. What we find in Scripture is the Sinai Tradition and the Settlement Tradition. We can then deduce that the earliest recording of the Exodus did not include the Sinai Tradition hence it not being mentioned in the earliest creed.
We can see the historical development in the end of Genesis and the beginning of Exodus:
Then Joseph took an oath from the children of Israel, saying, God will surely visit you, and you shall carry up my bones from here. So Joseph died, being one hundred and ten years old; and they embalmed him, and he was put in a coffin in Egypt. Now these are the names of the children of Israel who came to Egypt; each man and his household came with Jacob: Reuben, Simemon, Levi, and Judah; Issachar, Zebulun, and Benjamin; Dan, Naphtali, Gad, and Asher. All those who were descendants of Jacob were seventy persons (for Joseph was in Egypt already). And Joseph died, all his brothers, and all that generation. But the children of Israel were fruitful and increased abundantly, multiplied and grew exceedingly mighty; and the land was filled with them. Now there arose a new king over Egypt, who did not know Joseph.
So red is Genesis and blue is Exodus. Now note this:
Then Joseph took an oath from the children of Israel, saying, God will surely visit you, and you shall carry up my bones from here. So Joseph died, being one hundred and ten years old; and they embalmed him, and he was put in a coffin in Egypt. Now these are the names of the children of Israel who came to Egypt; each man and his household came with Jacob: Reuben, Simemon, Levi, and Judah; Issachar, Zebulun, and Benjamin; Dan, Naphtali, Gad, and Asher. All those who were descendants of Jacob were seventy persons (for Joseph was in Egypt already). And Joseph died, all his brothers, and all that generation. But the children of Israel were fruitful and increased abundantly, multiplied and grew exceedingly mighty; and the land was filled with them. Now there arose a new king over Egypt, who did not know Joseph.
Can you see now how we can find repeats and additions to the basic story. So we can posit that the original looked like this:
Then Joseph took an oath from the children of Israel, saying, God will surely visit you, and you shall carry up my bones from here. So Joseph died, being one hundred and ten years old; and they embalmed him, and he was put in a coffin in Egypt. Now there arose a new king over Egypt, who did not know Joseph.
Over time this was added to to become what we read today.