Whether you lost your Gmail username or are searching for the Gmail account of an associate, Google has search features that help you locate the information you're looking for. What's impossible, however, is to look up contact information for individuals you don't have on your contact list, as Google doesn't maintain a public database of its users' personal information.

Find a Contact's Username

If you need to locate the username of a Gmail contact, you can run a search by phone number. You can access this search feature by clicking "Gmail" on your Gmail page and selecting "Contacts" from the drop-down menu. Here, you'll have the ability to search for members of your contact list -- by phone number, name or address.

Recover Lost Username

If you have a Google Voice account, you can recover your lost username associated with the account by using the Google Voice recovery feature. Here, you can enter your Google Voice phone number to get the Gmail username associated with the account.