No that guy was a regular in old Garfield comics. I think he was Jon's roommate or something. In fact I believe Odie is technically his dog idk what happened to him.
After decades of absence, Lyman made his big comeback in the Garfield Show story arc, "Long Lost Lyman". In this continuity, it is revealed that he found work as a wildlife photographer. He had gone to Australia and searched for a mythological creature, but suddenly disappeared without a trace. When Jon, Garfield and Odie went looking for him, they had found him dressed as that creature. Lyman explained that he never contacted them, because there was no way he could. Lyman decided to stay in the jungle to protect the wildlife from poachers, but promises to visit when he can.