I believe when you lose your best doggy friend, they go to doggy heaven.
Later when you meet a friend/neighbor walking their dog and that dog treats you like a long lost friend, it has convinced me that there is communication between the dogs here and your dog you lost.
The dog here is telling you that your best friend is well and no longer suffers the pains of this world and all is well.
I miss my best buddy, and there are 5-6 dogs in my neighborhood that always let me know my bud is doing just fine.
Don't know about Angels but do know having dogs(especially BIG dogs) keeps the midnight theives from stopping by farms & rural homes in our area.
Helps to when you do come out for a vehicle you don't know(day or night) if you are carrying a rifle or shotgun. Word gets around - avoid the place. Dogs and crazy owner.