Few weeks back while I was making some changes to an old website, I noticed it was setup with Google Analytics but couldn't find the site configured in any of my accounts (well, the ones that I could of think of at the time). Luckily I was able to identify the account with Google's help.
Finding and regaining access to the account is a manual process. Support for Google Analytics is handled by the Google AdWords team so you need an AdWords account to contact them. If you do not have an AdWords account, simply sign up for one. You do not have enter any billing information.
Head over to the contact page for AdWords and choose the email option (or which ever option you'd prefer). Select Google Analytics, fill in the necessary details and describe the issue. Don't forget to include the tracking code. You should get an email response from a Google specialist within a day or two with the next steps.
Ideally, you would need to contact the administrator, but in your case, I understand that you're unable to place them - and for security reasons, we're unable to disclose administrator information to you. What I can do to help you is write on your behalf to the current administrator/s on this Analytics account, requesting them to get in touch with you.
If you would like me to go ahead and do this, please reply to this email stating so, as this will be the first step.
In case this doesn't help and we don't hear back from the administrator (within 7 days from when I write to them), I will share with you the steps to prove ownership of the domain(s) being tracked by this account, and thus gain access to the account independently of the administrator(s).
In my case, it was a Google account that I had forgotten about (created when my Google Apps account got transitioned to the new system back in 2011) so was able to reset the password easily and regain access. It was good to know that I could also regain access by proving domain ownership.