It's not all that hard to find the source of leaks yourself. In the future, at the very least, have them show you the leak while it's leaking so you can tell if they are being truthfull.
Pinholes do happen. More than likely it's adjacent to the pump or valvebody, so it's under hydraulic pressure, not gas pressure.
NO, your battery escapade did not cause this.
Just hate to see people lose mo' money.
