A properly made up EMT run is a grounding path. Did they also include a grounding conductor in the bundle coming in? If you really want a connection to the box and the installer wasn't polite enough to put a screw in the tapped hole you should be able to chip a little concrete out next to the box and use a clip. When I set the concrete boxes in my walls I ran a #10 screw a little longer than a typical "green ground screw" and put a dab of duct seal on the outside so I had a good void to install my ground screws.
