I got ripped too. Stay away from this scam.
The OP just posted that the transaction ended up going through fine. What happened in your case?
I opened an account with Coinbase a couple weeks back. I made 2 small buys so far. The first one went well. On the second purchase I bought right before the price went way back up and they sent me a notice that they had to cancel that purchase because they thought it was high risk somehow. They suggested trying back in a few weeks.
Usually if you contact them about a cancelled transaction they'll push it through. They're still training their fraud detection algorithm so that happens sometimes.