There can be no doubt where this dog's treasure is. Further, he is absolutely content with what he has. But all that he has can be taken away from him at any moment if someone were to close the trunk. True, he would be happy for a moment, but when he ran died of thirst, that would be that. Jesus said:
Matthew, Chapter 5 (WEB)
19 “Don’t lay up treasures for yourselves on the earth, where moth and rust consume, and where thieves break through and steal; 20 but lay up for yourselves treasures in heaven, where neither moth nor rust consume, and where thieves don’t break through and steal; 21 for where your treasure is, there your heart will be also.
Think of things eternal, for only those things can never be taken from you. That is the heart of the matter.