How I found this is quite a long story.
I'm the owner of a Jack Russell (or part Jack Russell, to be accurate). My dog was ahead in the queue when they handed out handsomeness and loyalty, but towards the back of the "Brains" queue.
Things my dog has detected:
1) Empty Tuna Cans with just enough tuna in to make it worth flinging them around the garden.
2) Left over rice. (He loves rice).
3) Something interesting behind the stacked paving slabs in the yard.
4) Toys he buried in the garden (as long as they were buried more than a year ago).
The Jack Russell in this series is certainly a far better detective (I reckon my dog would be in with a chance on the case of the Buried Biscuits, mind).
More information here I particularly like the French version, "Jack Russell: Détective Canin".
Written by Darrel and Sally Odgers, the series is published by Scholastic.