How long have you had this bass? Was it working fine before?
You can solder the crimp on in a pinch to get you up and running, then we can supply you with a pre-crimped wire you can splice (and protect with heat shrink tubing) later.
However, that still doesn't explain the symptoms you experienced. Even with one pickup completely disconnected, you should still hear the other one if the pan control was anywhere but 100% to the disconnected pickup.
If your tuner has an output, you should try leaving it in the signal path and see if you get the signal from the bass then. Let me know what you find.
There are some connectors on cables that overshoot the battery switch on the completely standard Switchcraft connector in the bass (strange, huh?). You can try pulling the connector out very slightly and see if that turns the battery on (and then of course you hear the output). If you try this, let me know what you find.
Leaving your bass in the car in any weather condition is not a good idea, mainly because that's where reports of stolen instruments happen most often. A sudden, dramatic temperature change can hurt your pickups in that the coil can pull away from the magnet and cause it to be microphonic, but it won't make a wire come loose.
