Today, a GPS device would have shown the alternate route, without even breaking my stride. Garmin makes several very lightweight and durable GPS handlebar-mount devices, with backlights for night, which come with an array of options depending on your needs. For around $300-400 you can buy a Garmin GPS 605 and for $100 more order a chip from their website with all streets in North America.
The Garmin 705 Bundle Model, which runs between $600-700 comes with cadence and heart monitor for optimum efficiency and performance, and comes with all the North American roads, plus the basics that measure distance, speed, time, etc. Not long ago, I purchased such a unit and took off on a 180-mile two-day ride and the Garmin unit was sufficient and helped out a lot, especially excellent was the elevation notations. This device also tells you your heart rate, best speed, and records the history of the ride, which you can download to your computer.