Chris wasn't aware that there was another way he could have crossed the river back to civilization. Describe how he could have done that in Into...

A passage detailing Jon Krakauer's own journey to the bus
where McCandless died explains that there certainly was a way in which the young man
should have been able to escape his death sentence.

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Unlike McCandless, however, I have in my
backpack a 1:63,360-scale topographic map (that is, a map on which one inch represents
one mile). Exquisitely detailed, it indicates that half a mile downstream, in the throat
of the canyon, is a gauging station that was built by the U.S. Geological
Survey...

We arrive to find an inch-thick steel cable
spanning the gorge, stretched between a fifteen-foot tower on our side of the river and
an outcrop on the far shore, four hundred feet away...hydrologists traveled back and
forth above the river by means of an aluminum basket that is suspended from the cable
with pulleys...The station was decommissioned nine years ago for lack of funds, at which
time the basket was supposed to be chained and locked to the tower on our side--the
highway side--of the river.  When we climbed to the top of the tower, however, the
basket wasn't there.  Looking across the rushing water, I could see it over on the
distant shore--the bus side--of the
canyon.

This passage is found
near the beginning of Chapter 17 and does provide additional information about the
basket and pulley.