The digger just set the mined item into the next empty slot.
It would be better if it tries to merge with existing items.

It.. it does.
That's how it works.

I don't get what you're saying.

this
https://drive.google.com/file/d/0Bxk8bebSTRk-cUUtOVV4LUhpcG8/view?pref=2&pli=1

I don't want to "fix" this, sorry.
It is supposed to work in the way that it always starts checking at the top left.
Changing this would make the code way more complicated and performance intensive and I don't actually like the way that would work gameplay-wise.