Tracy,
You cannot get contact that were NOT contacted using adv find, that is the limitation, you can only get contacts that you have contacted.
You can get the positive list of contacts (in positive way not using NOT IN) you last contacted on when but only if you have stored the last email date on the contact.
Let's say you have 1 contact, Adrian Jansen
You send email 3 times, 1 Jan 2015, 2 January 2015, and today.
You use that adv find to find contacts were contacted on today, fine, you can get it using the adv find.
You can change the date, you can see Adrian name.
But once you set that date to 2 January 2015, (you expect to not see Adrian, because last email you sent to him was today), you will also still see Adrian name because you set the date to 2 January 2015 and yes you contacted him, but, it is incorrect in your term, because you just by today sent email to him.
So the adv find with that query is good for you to help you to find out the list of the contacts you were sending email to whom on that specific date, but NOT for the LAST date, because if you sent that email after that specific date, that contact also appear, as I explained before, and CRM adv find cannot get the NOT IN criteria as well.
The most possible way to do, maybe it is too over data now, too late, you need to have a field in the contact, last contacted by or last emailed by.
Then everytime an email created and sent to him you update the field to the last sent email. You can use workflow or plugin oncreate email or any status you want
With that field you can find out contacts last sent email is which date. You can play around with this date field later, you can find out who you have contacted on last period only, not using NOT IN clause, but you can list contacts were contacted last month for example.
Hope this helps!
