I'm really thinking that it's not just coincidence that you had a tip called in the day after you confronted them...
What I'm thinking these sick sobs did was move Harrison to a safehouse of sorts until the heat dies down. Why turn the dog loose instead of being like, "Oh we've been caring for him and he's been a great house guest" and then handing him over? Now keep in mind, I am highly distrusting of other people and you can blow this theory off but people have gotten away with worse things than stealing dogs by lying.
I'd also probably start making signs that say the dog was stolen.
I think it's important not to make assumptions. Some people are just not particularly helpful. They may not like dogs, they may not like strangers, they may just be nasty people, they may have been having a bad day, etc. etc. While I think that filing a police report is not necessarily a bad idea, I am very glad that you are not jumping to conspiracy theory conclusions. When Boo was gone and we had a tracker with us, there was a man who refused to allow the search dog to cross his lawn, and was very guarded, but then made a stray comment that he "thinks he saw a black dog go that way." He was thoroughly unhelpful and didn't let us know about his sighting until he was physically approached (versus taking a second to call the number on the flyers plastered EVERYWHERE), but he didn't steal my dog.
Just be careful to dismiss the newest sighting because you're stuck on the idea that someone stole your dog. It doesn't sound like you're ignoring the sighting, but I just thought I'd throw that out there.
Dogs can sound similar. From my personal experience, I think that it is often easy to determine which bark does
not belong to your dog, but between similar barks, can be near impossible to know if it was your dog.
I'd say especially if you live in an area that is known for crime, I wouldn't be surprised if a neighbor didn't want to open their door the whole way. Heck, I live in a nice(ish) area, but if a stranger knocked on my door when I was home alone, I sure wouldn't open it if I was concerned about ANYTHING at all regarding the situation.
Good luck finding him. He's still in my thoughts.