You see a man lying still on the ground, blood pooling around his body, and a woman standing close by gripping a knife with bloody hands. What happened? “We weren’t there. We didn’t observe it.”
She tried to save his life by removing the knife, then she went in to shock? Probably not the explanation you had in mind. This is not a good metaphor.
You see? You are still able to make theories based on what you know and causality, and we can debate about which theories are most likely to be true. Not directly observing something is the beginning of theorizing. We don't just give up on knowing.
That only works because humans have killed each other, not to mention animals, many times in the past, so all of us are familiar with the process. We're yet to observe any instance of abiogenesis at all, anywhere.
We don't merely make predictions based on patterns we currently observe. We also make predictions and reason about the past based on reason, causality, and other theories we can demonstrate to be true.