Professor Solomon's "How to Find Lost Objects" is the companion website to a book of the same name. I lose stuff all the time, largely because of all the travel I do (jetlag plus lack of routine plus strange places plus airport security equals plenty of opportunities to lose your shit, literally). The practical tips here are just the kind of advice I wish someone would give me the next time I'm hyperventilating over a lost passport.
Objects are apt to wander. I have found, though, that they tend to travel no more than eighteen inches from their original location. To the circle described by this eighteen-inch radius I have given a name. I call it the Eureka Zone. With the aid of a ruler (or a Eureka-Stik–click here for instructions on making one), determine the Eureka Zone of your lost object. Then explore it. Meticulously.