identify similarities in a dataset
In general identifying similarities is done with clustering, but in this case what you're looking for is a potential pattern in the data leading to a missing value in a specific column, right? So I would try to train a decision tree using all the columns except the target one as features, and using a binary class indicating whether the target column has a missing value or not. Visualizing the decision tree obtained after training  should show the pattern if there is one.