Being a total newb - im not sure what Escrow is or how to tell if I used it. I presume its some kind of middleman who holds the funds for both parties until buyer is happy - then releases. Which would be a great idea if I had known there were these kinds of services out there.
I purchased the bitcoins through a vendor on localbitcoins.com, who have always been extremely good. I transfered the payment to samsungstore from my balance on localbitcoins.com which keeps a virtual wallet for you.
Could I approach them for help? Or try and insist they investigate? Or do i not really have a leg to stand on?
There is nothing they can do. It doesn't matter where your wallet is (even your own wallet) Bitcoin is designed to be irreversible.
Imagine you handed a stranger with no name, address, or ID, a bag of cash with $300 USD inside and he said "wait right here I will be back in a couple days with your phone", two days pass and the guy hasn't shown up. How would you reverse this transaction?
Sorry for you to learn the hard way, but in the future before clicking [Send] ask yourself "
do I trust this person and know enough about them that I would hand them a bag of cash and know they would delivery?" If the answer is no then don't send your coins. It is the EXACT same thing.