Christians: Please explain the Exodus

[Jackalope]

Actually the Bible does say that God supernaturally made it so no trace would be left:
Deut 29:5 5 Yet the Lord says, “During the forty years that I led you through the wilderness, your clothes did not wear out, nor did the sandals on your feet."

Nothing wore out, so nothing to leave behind.

So their graves should not have worn out, nor their altars, nor their huts, nor their pottery. Where are they?

Magic, obviously - and when you've got magic on your side, you can't rule out anything, so obviously anything is possible.

Derp.