
I'm sorry you have had to put up with such worry for your little pup, it says a lot about the state of this place at the moment.
Both my dogs are adults now (well, physically anyway :P) but I do still worry about them being stolen - regardless of the fact they are both neutered. Dogs are still stolen for pets, sadly. It's sick really, taking someone's beloved pet to make a few quid. I do walk mine by myself, but luckily I'm not in a big dog theft area (with the exception of a couple pups and a Yorkie to my knowledge). Plus, they are a male doberman and a female rottweiler X - I'm sure they would protect me if anyone tried to hurt me to get at them, and whilst they are both very friendly with strangers, I know they'd kick up a hell of a stink if someone tried to take them away from me, the rott X especially. I'm still careful though - I don't leave them in the car unless I can't help it, and then I make the time as short as possible, and I never leave them outside a shop, even if I can always see them. I worry the most about the dobie - he is a fawn, so a "rare" colour to most people. The future holds more of the same I fear - I am looking at Utonagans at the moment (wolf lookilikes), and I suspect they will be of great interest to many people who will probably assume they are wolfdogs. Sigh.
As was suggested, do keep someone else with you, and get pup chipped - both mine are, they also have a tag on their collar (as well as the normal one) saying "I require daily medication" - I've heard of that putting off potential stealers before, as medical problems obviously detract the value of a resale dog.