there is a spring on the other end of the butterfly shaft were it connects to the jet pump that should turn it to full open.
I think you mean "closed".
For the times I have seen a throttle shaft spring, it has been arranged so that if the throttle shaft were to become free (linkage disconnected), the spring would move the shaft toward fully opened, or full power. Similarly, I have seen springs on the mixture which would move a disconnected mixture arm to fully rich. Though loosing control of the engine power is undesirable, if you must loose control, you'd rather it be to high power than idle or stopped. For a turbocharged engine failure to full open throttle could also be bad, but I suppose a little less bad than the engine stopping at that point.
A known failure point has been a worn spherical rod end from the throttle cable to the throttle arm. If worn enough, the chassis of the rod end can pop off the ball, and you just lost throttle control. This would nearly never be a part of a pilot daily inspection for lack of easy access. So it is very common that a large diameter "penny washer" be added to the rod end bolt beyond the spherical rod end, so if it does fail, the chassis of the rod end is still captured somewhere around the ball, of not over it. You'd still have control of the throttle. Unfortunately, I have seen carelessness in reassembly, and this is missed. A carburetted Continental 550 engine was replaced in a C 182 amphibian I used to fly. I was visiting, and the owner mentioned this to me. He asked if I'd help with the oil change (during my social visit, but okay). I watched, they got dirty hands. As I looked around, I saw that the engine installer had indeed placed the penny washer on the wring side, and failure would have been possible. This was among several errors under the cowl.
So if the cowls are off your plane, it's worth a look around, and ask questions if there's something which does not look right!