It appears you are running Premiere Pro CS6. Duplicate Frame detection is a feature of Premiere Pro CC, not CS6. Sorry!
What the ... ?!?!
Sorry, I've been out of the Premiere loop for a while.
What the heck is Premiere CC? Creative Cloud?
Is that "newer" than CS6??
Do we need to upgrade?
What are the differences??
Yes, Premiere Pro CC is the latest version of Premiere. It was released last month. view these links for all of the details.
Premiere Pro CC features:
Creative Cloud FAQ's:
Calling it CS7 maybe less confusing to the poster.