but how did there dog find the body it was not aa trained tracker dog.
The same as it would smell out a dead rabbit - luck. But that is the problem, an untrained dog, would just go off and sniff out anything, the training makes them focus on the thing they are supposed to be looking for and ignore other distractions. A trained dog sniffing out drugs would ignore some lamb chops for instance whereas my dog, would just eat the lamb chops.