If it is still cooling then it is not a refrigerant leak and leaks don't come and go. 134A is considered not harmful to the environment. Where it is deadly is it displaces oxygen and is considered an asphyxiant. I think it might be more of the glues or adhesives during assembly.
If you had a hissing sound loud enough to hear and it was a refrigerant leak it definitely would not work anymore. I don't know how the controls work on the CR-Z but some older vehicles used vacuum tubing to actuate the doors and valves in the heater / A/C box under the dash. The way the car generated this vacuum was small black tubing off the motor. What you are hearing could possibly be these actuator relieving this vacuum to move a door or a valve and the smell could be the "engine smell". The best thing to do is take it to the dealer if you are concerned.