Is ebay likely to make me refund the buyer as there is no tracking which I think is unfair as buyer chose not to pay for tracking?

As the seller it is up to you to post in a safe manner to meet paypal requirements, and to protect yourself for something like this, especially for overseas parcels.

Yes, paypal will find in favour of the buyer if you can not prove 'postage'.

However,  you have the receipt for 'Russia', call paypal and ask them for assitance in answering the claim.