CAVirtex implements what is referred to as a hosted (shared) EWallet service. So you have no control over the bitcoins with you withdraw, you are simply submitting a request to CA VirtEx to withdraw and it is up to them to service that request.
In nearly all instances of legitimate activity your client will know of the withdrawal withing seconds once CA VirtEx broadcasts the withdrawal to the Bitcoin network. So it is pretty safe to say that if you don't see your withdrawal on the blockchain then VirtEx didn't send it.
This can happen if the EWallet provider uses cold storage for coins, and the current level of coins in their hot wallet is insufficient to serve the demand. The delay will vary based on approach and security practices surrounding the cold wallet. For instance, a competing exchange in Europe can only access the cold wallet during business hours since access requires physical access to occur at a bank vault.
There are instances of spam-like activity where a transaction is sent and peer nodes refuse to relay it right way. That's not the profile of a withdrawal fro CA VirtEx though so that's not likely what happened here.
tl:dr; wait a bit longer. If you wait more than half a day and still don't see the withdrawal, then contact the exchange.