What is the ruling regarding someone who saw a dog licking a body in the street, then passed by the same body and predominantly assumed that he touched it, and is it obligatory to inform him that his clothes have become ritually impure?

The body becomes impure by a dog's lick. If the body remains wet and touches a garment, the garment becomes impure. However, if both the garment and the body dry, the impurity does not transfer. It is necessary to inform anyone whose garment has become impure if it is highly probable that the impurity has transferred to it, as this is obligatory according to some scholars.