If you can't contact the recruiter, there's a chance that the hiring manager can't get in touch with him either. In normal situations, trying to go around the recruiter is a definite no-no, as it shows bad faith both on you and on the part of the company toward the recruiter. In situations where you cannot contact the recruiter, I would take the following steps:

1. Try contacting the recruiter again
2. Try contacting the recruiting company
3. Consider sending an e-mail to both the recruiting company and the hiring manager relaying the situation

###Contact the recruiter again

If you can't get in touch with the recruiter by phone, try e-mail. Try calling the office and getting transferred. Try any means that you have to get in touch with him directly. Most professionals who have time-sensitive jobs will have an auto-reply if they're out for some reason or another, or the office can let you know if they've been hit by a bus, left the company, or something else.

If you cannot get in touch with the recruiter, or anyone else who knows the status of your application with this company, I would suggest taking the next step.

###Contact the Recruiting Company

Assuming this isn't a one-man operation, there should be other people at the company. Try to get in touch with the boss of the recruiter you were working with, and do your best to explain the situation. It is possible that the recruiter quit unexpectedly, or didn't tell people what the status was prior to going on a vacation to Borneo, or has been out with the martian death flu and nobody is quite sure what the status of all his responsibilities are.

If you cannot get in touch with someone in a position of responsibility within the organization, or you are otherwise not given an answer that indicates that they are on top of the situation, then move on to the next step.

###Consider Contacting the Hiring Manager

Chances are the hiring manager has enough information on you to contact you if needed. If you have added your e-mail, phone number, web site (with a contact form), or anything else on your resume or application, then they can get in touch with you. Chances are that if you haven't been gotten in touch with there are one of two reasons:

1. They haven't made their decision yet
2. They are in touch with the recruiter even if you aren't

If for some reason you strongly think that they have no way of getting in touch with you, and they have made their decision (for instance, you were told during the interview that they will definitely give you an offer by date X, and it is past date X), then you may want to consider contacting the hiring manager by e-mail. Let him know:

1. You were unable to get in touch with the recruiter
2. Attempts to find out the status through the recruiting company were unsuccessful
3. You are not trying to circumvent the recruiter, but just want to make sure that your contact details are available to the hiring manager just in case

I would CC the recruiter, and the recruiting company manager you spoke to so that everyone is exactly clear about what is going on. If you do this, bear in mind that this will make the recruiter look like they are not doing their job, and that the recruiting company is not managing the process well. And that probably isn't a great thing to do if you are going through the recruiter for other positions, or if you have some connection that recruiter through your current job. And making the recruiter look bad also implies that the company who is using the recruiter made a poor decision, which also probably won't look good for you.

So if you do decide to send the e-mail, be very certain that you aren't just jumping the gun and pestering the hiring manager before they've had time to make a final decision.