They wandered the desert 40 years subsisting purely on McDonalds 60% hair-free goat burgers. GPS technology, unfortunately, was not advanced as it is today (neither was the fast food industry).
The Bible Spoof reveals in fact it was Miriam, Moses' big sister, who led the Children of Israel out of the desert. It took 40 years, as she simply couldn't read maps. She could, however, change diapers and is credited for developing the washing powder "Exodus" having had to wash Moses' nappies in the Pharaoh's pool in Akhet-Aten.