I got my dog that way. I never thought I would have a dog (as I'm a cat person). However, he showed up covered in oil and under weight. So I took him home (rookie mistake) and bathed him. I went out looking for his owners. I took him to the vet and he was microchipped! So they called the owners and they hung up on the vet. He was only like 7 months old and a small dog. So I adopted him. He's super sweet and smart and calm. I can't imagine anyone who would just abandon a puppy.
It also really makes me sad that he's terrified of the broom. The dog loves me. I'm his safe human and if he gets scared he runs to me. If I even put my hand on the broom, he tucks his tail, gets low to the ground and tries to get out of the room.
People just suck sometimes. On the flip side, he's now my constant companion, slightly neurotic and super awesome. I became that person with dog pics on their phone. He's really my ideal dog. So their loss was totally my gain.