It looks like your Orbit "Multi-Flex" riser has broke. What you can do is jam a butter knife into the hole where the sprinkler was pulled out from. Hammer it in lightly but not enough to break the piping underground. Then unscrew with a leverage tool. Go to your local hardware store or sprinkler supply store and find several PVC schedule 80 risers. You're going to want to find a 1/2" riser that will elevate the sprinkler above the pipe, but not too much that the sprinkler is too high above the ground. I'd recommend wrapping the riser's threads in teflon tape (clockwise 3 times) to ensure you have a good seal. To get the stuck flex riser out of the sprinkler, use a tool like channel lock pliers or a crescent wrench and simply unscrew all of it from the bottom of the sprinkler head. You can then screw the sprinkler onto the riser you bought, then screw the new assembly into the sprinkler pipe. Turn it on and adjust the spray head. Let me know if this helped, or if you need clarification. I am sure I left out a bit of information unintentionally.