The latch system is cable operated. When you pull the handle in the car it pulls the cable and releases the latch.
Is the cable detached from the lever inside of the car? If it is, try to reconnect it, or get some pliers to pull the end of it and pop the hood. Another way that is a little more barbaric is that you can cut the sheathing away from the cable and manually pop it by accessing it in the drivers side wheel well. If you decide to do this, I would suggest replacing the cable as it will most likely rust once the sheathing is gone.
