In every lawsuit the Plaintiff has the obligation to notify all defendants that they are being sued. When a lawsuit is filed the court issues a summons which must be served (usually with a complaint) on every defendant. Massachusetts and probably all other states prefer that the person be served in hand or at least by leaving documents at their home. What happens if you don't know where they live or work? How do you serve them?
Every state has laws that allow a substitute form of service of documents on a person who can't be located. In Massachusetts, a motion must be filed to serve by an alternate form of service. If nothing else works, the court can order service by publishing in a newspaper. Of course, most people don't read the legal notices in newspapers so service by publication usually results in no notice at all but would be satisfactory to a court. In Massachusetts, the courts prefer that a different form of notification be used. Massachusetts courts now require detailed affidavits explaining how the Plaintiff searched for a Defendant including details of searches on the internet. As one clerk told me internet searches are required unless the Defendant's name is Smith.
A search for a missing Defendant should start with a search for a telephone number. A telephone information request with the telephone company is generally a first step. If this doesn't work, a similar search on the internet using multiple search engines (Google, Bing, etc.) should be made. If the person has a driver's license or professional license then the state data banks may show a current address for the person. All of these search methods may show a residence for a missing Defendant. A lawyer can request confirmation of addresses or forwarding address information from the post office. A non-lawyer probably would need a court order authorizing the post office to provide this information from the post office.
If, after using all of the methods just described, the person still can't be located, then social media should be searched. There are too many social media sites to search them all. At a minimum, Facebook, Linkedin, Instagram, and GooglePlus should be searched. If a social media page is located for the individual then print the contents of the page. A judge may need information that the person currently uses the social media site.
If after all of these methods, the person still can't be found, try to locate a close relative: parent, child, ex-spouse, or sibling. These people may be in contact with the person and may be used for service.
After all methods to research have been used and if you still don't have a work or residential address, then file a motion with the court for alternate service. In Massachusetts, and probably other states, the judge will want to use the best method of service that is calculated to actually reach the Defendant. Service can be made by email, text messaging, messaging through social media, or by relatives. The motion should be accompanied by a detailed affidavit showing all of the internet research and any relevant web pages.
If after all of these steps, the person can't be located, service by publication may be approved by a judge. Service by publication is expensive and usually ineffectual. However, it may be the only method available. Alternate service can be complicated for individuals. A local attorney can guide you through the process and help you locate your defendant.