You don't need to have any direct relationship or even knowledge of mutual existence for trade to happen.

Person A sells to person B, person B sells to person C. You then have a trade route from A-C without them having to interact. Items can be traded across entire continents in this way. A modern example is 'un-contacted tribes' wearing western clothing because a contacted tribe used those items for trade.

It seems extremely unlikely that the Myceneans knew much about Scotland, if they knew it existed at all, since by the 5th c. BC Herodotus is still sceptical about the existence of the British Isles, even by the 3rd c. BC it's still not clear whether the Greeks understood the distinction between mainland Britain, Ireland and Scandinavia. When they are mentioned it's often in relation to trade (the place where our copper, tin etc. comes from...)

The idea that the Mycenaeans, or any other Greek people pre the 1st c. BC knew all about Scotland may have come via the maverick theories of Samuel Butler. He was a Victorian classicist and translator who most famously translated Homer. He had a few pet theories which aren't at all accepted by mainstream scholars but which are quite fun.

One of these was that The Iliad and the Odyssey were partially based on historic events which took place in the British Isles, in particular the accounts of how chariots were used, and that these stories travelled to Greece where they were written down.