Yoda's trying to get the hell outta dodge. He got his butt kicked. He crawled away with his "tail between his legs". What Yoda taught Luke on Dagobah was with remotes and a few metal bars that he took from the escape pod. He never trained Luke how to fight with a Lightsaber, per say. He tested and honed Luke's reflexes. If he really trained him with a Lightsaber, Luke would be fighting more like the Jedi used to, rather than the way he does later on. Anyway, Luke's training on Dagobah was only see in the novelization and the Marvel Comics adaptation. Both versions did not show Yoda using a Lightsaber. I don't know what the current young adult adaptations, which were written in recent years, would say. Well he didn't have it in the films. In the eu, he did, but he lost it at some point or decided to never take it out again. Yoda did just fine for 20 some years without a Lightsabers.