Opening a case with paypal and ebay?

Ok, so basically on the 21/04/14 I bought an iphone 5s off a seller (on ebay) as we negotiated a price we came to an agreement to. The item was on bid and since it was on bid we decided to do the transaction on paypal. Now before I carry on, I hold full responsibility for carrying a transaction outside of ebay and I accept the issue is no longer in their hands. It's just that when I was offered such a good deal that fitted my budget i was willing to seize the oppurtunity.

When the seller and I were negotiating a price she responded very promptly and on time, and after I made the transaction she never responded once. Its been several days since I ordered the item and I am certain I have been scammed because today and a couple days ago, 2 sellers have left negative feedback stating the seller is a thief and have also stopped replying to them. (At the time I ordered there was only positive feedback)

Whilst negotiating a price she said she will provide me with the tracking number and till this day I have received nothing.

Will paypal ensure she refunds my money. She hasnt responded to me since I have made the transaction

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