Dumbfounded

This afternoon, we got a phone call at work that we get at least once a week. "Hi, um, I just found this dog and his rabies tag came from you guys, can you please help me find the owner?" We always get the person's information and try to make contact with the owner, or if the finder has no way to take care of the dog, we offer to let them drop the dog off at the clinic until we can contact the owner. The person who finds the dog is always a Good Samaritan who 'just can't stand the thought of this dog being hit by a car!" And the owners? They are usually in tears, thrilled to be reunited with their dog, and gratified that people cared enough to work together to keep their pet safe.
This case started the came way, but quickly became much more complicated. We tried every phone number in the computer with no answer, but left messages on the machines. We dragged out a phone book to see if their we could find alternate numbers for this person. Meanwhile, the person who found the dog was becoming upset- the dog was large and she had nowhere to put him, and could not drive him to the clinic to stay because her car was in the shop. So, despite being understaffed on a very busy day, one employee went to get the dog. The woman who found him was so grateful- right next to a busy street, she was terrified that he would get away from her and be hit by a car.
Finally, the owner called us back.

Was he:

a) Thrilled that we found his dog

b) Thankful that we put such an effort into keeping his dog safe

c) Angry with himself for losing his dog in the first place

d) angry with the neighbor for calling us, and angry with us for providing the dog a safe place to stay, since the dog was "still in the neighborhood, I would have found him eventually!"

You're thinking the answer couldn't possibly be d, right? That I threw that in to be funny? Well, the answer is d. Tell me, why do we continue to help people when they are so unappreciative?