We're constantly bombarded with information. Radio, TV, Web, email, phone, fax—the list does go on. With a fairly high noise-to-signal ratio, we have all become pretty adept at filtering-out most of this stuff. That's all well and good, until you realize that you just missed that vital piece of info that went flying past.
The ad plays on the radio. They give you the number to call—once, twice, three times. It's just as that final recitation of the "where to call" fades off into the distance that you realize "Darn! I really need to new widget, and those guys are selling them. What was that number anyway?"
OnTheRadio.net has a commercial-finder service. If you enter enough of the particulars about your missing ad into their Web form—the time the ad played, the station you were listening to—they claim to be able to help you find your commercial. We tried several times, but were unfortunately met with the sad message "Only radio stations that have commercials registered are shown." Clearly none of our stations were registered, so we never got to find out what the missing phone number was. Hopefully they'll register more stations in the future and help you find your missing ads.