He almost went back.
As soon as he got home, he knew he had done the wrong thing. Libby would've scolded him for giving up their child for adoption. But Libby wasn't here. She had disappeared along with a host of other elemental masters. The police had given up. She was just another cold case in a stack of many.
Cliff wandered into Jay's room. All of his things were still there. His toys, his clothes, his crib. Cliff should've never given up his child. He had some money from when his mom died. He could've hired a security guard or two. He could've moved to a safer home. He could've tracked down the crazy guy who convinced Libby and Ice to fight a war against a bunch of snakes. But he didn't.
He sold the house. He couldn't stand to be there without Libby and Jay. Their things were put into storage. He had some money from a headache commercial he had done and moved into an apartment in Ninjago City. It was small, plain, and lifeless without someone to share it with.
Almost exactly a year after he had left Jay on the steps of the trailer, Cliff found himself back at the junkyard. Jay was busy playing with his new mom. Cliff told the man who ran the place that he needed props for a theater show. When Jay did finally notice Cliff, he didn't recognize him. He wanted to explain who he was and why he was really there. He wanted to grab his boy and take him home. But he didn't.
He tried anything to fill the void in his heart, but nothing worked. He managed to land a huge role in a space ranger movie, but it was meaningless without Libby and Jay around. There had been a handful of dates over the years, but nothing ever came of it. No one could replace his Libby. He wouldn't let anyone in and resigned himself to a lonely fate. When he turned the news on one day and saw a bunch of ninja running around, he immediately recognized one of them. He wished he could tell them why they shouldn't be flaunting their powers. He wished he could grab Jay and keep him safe. He wished he could go back in time and undo his mistake. The most he could do was leave his son in his will. When he suffered a stroke, there was no one around to help him.
He almost went back. But almost isn't good enough.