Welcome to Android Central! Sorry you lost your phone. Someone actually tested the remote erase on
this thread, and said that no confirmation email was sent. So there's no way for you to know, unfortunately.
Did you have a lockscreen set on your phone? If so, and if the lock PIN/password/pattern was robust, then it's unlikely the thief can break in and steal your information. More likely than not, the thief is more interested in just doing a hard reset and using the phone for himself. Do you still have the box for the phone? If so, report the phone as stolen to the police and to your wireless provider, and give them the IMEI. The provider should then put that IMEI on a blacklist, preventing anyone with that phone from activating it again.