It is every parent’s nightmare: a normally reliable child sets off on a journey, then vanishes without a trace. But through the power of social media, a small army of thousands of volunteers produced a happy ending in the case of Jacob Boehm.

Mr. Boehm, 22, a senior at Stanford University, had gone to Japan in June with the Stanford Chamber Chorale. When the rest of the singers headed home, he continued to travel, carrying his U.S. and German passports.

Like most of his peers at elite universities, he was well plugged in to the world around him, posting regular updates every two to three days on his travels through Southeast Asia. By Aug. 13, he had announced through his Google Plus page that he was in Malaysia.

Then nothing for a week.

Worried, his parents, Bruce Boehm and Nancy Luberoff, got in touch with U.S. and German consular officials in Malaysia and sent e-mails to 12 of his friends. The message went viral. On Facebook, more than 5,000 people subscribed to one of two pages dedicated to the hunt. On Twitter, #JacobBoehm became a trending topic in the San Francisco Bay Area, the home of Stanford.