I know this sounds harsh, and I don't mean it to impugn the compassion of any individuals who work in U.S. Embassies, but if you believe (as I did before my brother disappeared) that looking after the safety and well-being of individual Americans is part of the Embassy's mandate, this is an illusion you have to get over immediately. It will only lead you to greater frustration and cause you to waste precious time in the early hours and days of your search.
As far as I can tell, Embassies exist primarily to ensure that certain interactions and transactions between governments and among governments and large corporations happen as smoothly as possible. Anything that complicates this mandate is a distraction that must be gotten off their plate as quickly as possible.
When Joe disappeared in Honduras, I expected that when I called the Embassy to report him missing someone would take a big blue binder with silver letters saying Missing Taxpayer SAR Standard Operating Procedures off the shelf and start telling me how we were going to proceed and what the State Department needed from me to make the search and rescue proceed smoothly. Rather, I got multiple versions of the same question: "What do you want US to do?"
Make no mistake: Embassy staff are neither prepared nor inclined to spearhead a search for a missing person. And yet they must make you believe they are, lest you talk to anyone outside the State Department. They will tell you they should be your only point of contact. As the person in charge of the search and rescue (yes, YOU are in charge of the search and rescue) it is your right and responsibility to talk to anyone and everyone who can help you find your missing loved one.
Which leads us to the other reason Embassies exist: to insulate the Secretary of State from complaints from People Who Matter. People Who Matter primarily include U.S. Senators, Representatives, and senior executives of major corporations. This is why your first action (after notifying the Embassy of your loved one's disappearance and finding out whatever information you can from the person you speak with) should NOT be to work your way up the Embassy food chain, but rather to immediately engage People Who Matter on your behalf. The most obvious PWMs are your Senators and Representatives. Not as obvious but essential to getting action are the Senators and Representatives of everyone you know. If you have family members and friends in other states, get them started calling, e-mailing, and faxing their Congressfolk. All three mechanisms -- phone, e-mail, and fax -- are essential, because they make you impossible to ignore. Call first - if you don't get action, shift to e-mail and fax. If you still don't get action, repeat the ritual.
Make sure the people you have calling understand the circumstances (especially location, date, and time of disappearance) and the action you want taken (search crews on the ground, search planes and helicopters with thermal imaging and high-altitude, high-resolution cameras...whatever is needed). You have to be as clear to these people as if you were giving safety instructions to a four-year-old. And you must document every single interaction and be able to make reference to the people you spoke with by name and title.
Other PWMs might be the CEO of the company you work for. It might be the president of your university. If you work for a large international corporation, you probably have access to a VP in charge of security who is very likely in regular contact with FBI and State Department staff (particularly the Embassies' Regional Security Officers). Access these resources as quickly as possible.
If you don't know any PWMs, contact the people most likely to know some: your lawyer, accountant, financial adviser. Use social media tools like FaceBook, MySpace, and Twitter to build awareness of and support for your search.
During the inevitable downtimes between phone calls, e-mails, and faxes, brainstorm with your team as to who you know who might be of value in this effort: military types, corporate types, government and academic types, law enforcement types, ham radio enthusiasts, journalists, boaters and pilots (not that you expect them to go search, but they know things you don't know), and anyone who might have family in the country or region your person is missing in.
You might feel alone and overwhelmed, but one thing I have learned in my search for Joe has been that you have resources (internal and external) that you never imagined. Be strong and stay focused.