A few years ago, playwright Ken Urban saw Sam Shepard in a New York bar, near a theater where a Shepard play was about to open. Though he was a huge admirer of Shepard, who died last Thursday, Urban did not try to engage him in conversation. “I smiled and said hello and he smiled back,’’ Urban recalled Tuesday. “But he was in previews, and I know that look when you’re in previews.’’ Urban, 43, will soon be wearing that look himself: The world premiere of his play “A Guide for the Homesick’’ is scheduled for Oct. 6-Nov. 5 at the Huntington Theatre Company. But Urban has another reason to be in the Boston area: He’s been named senior lecturer in theater arts at the Massachusetts Institute of Technology, where he will teach playwriting. Urban, who taught at Harvard from 2006 to 2014, acknowledges that the reaction of some to his new post will be: “Theater? At MIT?’’ But the reality, he maintains, is that “Theater arts classes are the most popular class after all the engineering classes at MIT.’’Don Aucoin can be reached at email@example.com.