Anything that had a autograph or a drawing hasn't had a survey sent out yet. Probably other catagories as well.

To see if you should have had a survey but didn't get it for some reason, go to the Kickstarter Drive page, check your pledge level and see if it says something like this at the very bottom of it:

Survey sent: XX/YY/ZZ

With XX/YY/ZZ being the date it was sent.