How does Find My Mac work exactly?
I am assuming that you clicked on the option to "Erase your Mac" when you activated FMM.  If you got a message that the machine was erased, then the drive was erased.

As for the HDD, filevault does offer good protection against the most common of thieves, but nothing is perfect.  Chances are they can't crack the encryption.  However, if you wiped the drive, this is moot.

Is the machine "bricked?"  I don't know.  Did you lock it with a PIN code?  If you didn't, it can still work.  However, if you locked it down with a PIN, you have effectively bricked it.

Now...did you file a police report?