My Yugioh cards were scammed over YouTube?

Ok, so I made a deal with this guy on youtube and we decided that we would trade some yugioh cards online. Because he seemed like a trusted trader, I sent first. I sent about £100 worth of cards to him and it's been over a month, yet i've received nothing. Not only that, he closed his account when I asked him about the sent cards. He lives in America and I live in the UK. I still have his address, but since we live in different countries, it's going to be really tricky to resolve the situation. What can I do to get my cards back?