If you've not got your transaction ID you can check on the status of your tickets by entering your email address or post code here:
https://www.viagogo.c...TrackTransaction.aspx
However you need to be aware that Viagogo don't sell any tickets. Buying through their website is similar to buying through eBay. i.e. you're making a purchase from someone else who holds the tickets, with the website acting as an agent (and guaranteeing the process). It's the person who offered the tickets through Viagogo who should be posting them to you, not Viagogo.
That means that, just like eBay, there are some fraudsters who advertise things that they don't actually have. If your tickets don't arrive, Viagogo promises to refund your money, but there's little point in currently hassling them directly about your tickets (since they never had them in the first place).
Chris