You have got hold of the wrong end of the stick (so to speak)
The Dog won't be sick. It will .....(how do I phrase this) speed up the digestive process after some time!
The Dog will be home by then and will "decorate" his owners abode.
Apparently the dog will be non the worse for ware, but will be unlikely to re-visit the scene again!
Tallow is just a type of fat! Is there a law about leaving pet food in your own garden?