Left outer join missing values

I am using a left outer join to match two tables according a index. I need the nonmatched from the first, to calculate some rate. The problem is that, when I expand, the rows that should come with null values just disappear. This wrong in a lot of sense, since will become a inner join. 

Before expand

After expand:

Where is zero????????

This is so wrong. I will miss a entire work when if I don't fix that.