If you have searched for your Guardian and have had no luck in finding him, look for a nearby portal.
Once you find the portal, ask for the assistance of a UES.
A UES should appear, now ask the UES where your Guardian is located. The UES should tell you, if the UES refuses to tell you, then call on another UES. If there is no other UES, find another portal and once again call for a UES.