Absolutely. To change the left side injectors they have to drain the cooling system and remove the pipe that the upper radiator hose hooks to. They probably disconnected one of the heater hoses to make the right side easier. They may also have dislodged one (or more) of the injector sleeves. I would try to see if you can tell where it is leaking so you can prove that it was related to the injector service otherwise they will probably lie about what the problem was and make you pay to fix it.