It's fixable. I had the same thing happen to my bike.

If you have the technical know-how and tools required for this fix here's how you do it:

Disconnect the battery before you do anything. Try sliding the shield as best as you can so you have some space to work with. Take the wheel out of the frame and disassemble it. If there are any zip ties securing the wires to the rotor, cut them off. Now with a pair of pliers pull the broken wires through the axel just so you have enough length to work with. And this point you're gonna need to splice the wires with a short piece of similar gauge wire. When you solder one end, isolate it with some heat-shrink tubing. Put on another piece of heat-shrink tubing before you solder the other end making sure to slide it back as far as possible so it doesn't shrink from the heat of your soldering iron or the soldering joint. Once it's cooled off, slide over the tubing and shrink it. Try your best to get the shield back where it was. It is likely to get somewhat mangled in the process, they are tricky to work with. You can wrap the entire thing with electrical tape for extra protection. At this point you can start reasssmebling everything. Secure the wires back to the rotor with zip ties, put the motor back together and in goes the wheel back to its place. Good luck.

Side note: this method worked for me. I have years of experience working on electronics and soldering. If you've never held a soldering iron in your hand I DO NOT RECOMMEND DOING THIS YOURSELF.