I was just re watching seasons 1 and 2 of angel, and This character was in a few episodes ( played by David Herman), and I just have to wonder what happened to him.
Maybe he eloped with Kate, who also disappeared around that time.
He no longer needed the services of Angel Investigations. Or they decided to move away from the whole "Vampire running a detective agency." angle to the "Misfit Champions of LA" angle, and he was lost in transition.
Or Angel got hungry one night. ;P