Great news you must be so relieved.
One of our collies was taken ill suddenly some years ago, turned out she's got hold of the remains of a rabbit which had been poisoned. She was a bit of a scavenger anyway and being out and about most of the time (working sheep for a farmer friend) she had the opportunity to 'snack'. She recovered that time but we lost her during the foot and mouth year. Someone in the village had but down commercial poison for the vermin which were a real problem then, unfortunately Gyp was not so lucky that time.