It is not a spring per say, at least the coiled kind most think of. It is a plastic finger link piece that is attached to the trigger, which acts like a spring/resistance. I would say if yours is not springing back into normal position (where the trigger cannot be pressed all the way without pressing the lower part of the trigger first) then it is broken or bent back. You could press out the small pin in the trigger (the one where it would be the pivot for the lower and upper trigger), you should be able to remove the lower part and inspect it. You could press it out without disassembling the gun, but I would at the very least is make sure it is unloaded and remove the slide as a good safety habit (even if you know the gun is unloaded). If it is just the finger/spring that is bent, you may be able to heat it up a bit with a hair dryer and move it back into position.