I agree, this is the most logical explanation. I think after taking drugs he felt full of energy but after a while the terrain got more difficult. When he attempted to retrace his steps, he got more lost, because a lot of the paths look the same. It's likely he went down in altitude, instead of up, into the shade, which could be why he said he is "surrounded by mountains". Whereas if he went up, he would see that he is not far from settlements.
People have compared this to the Michael Mosley case, but this young man has a big physical advantage compared to an older person and this climate is more favourable for survival, but it involves finding a water source. They do exist here (See image taken from Flickr of the Masca ravine), but getting down to it could be dangerous. His family have described him as street wise, but being street wise is no use in this landscape.