Maybe it all depends on the willingness of bystanders to help stop the thieves. Evidence from big cities is not encouraging. Most willingness is encountered on airplanes, where one terrorist can easily kill all passengers, but even there, it seems to take an example for others to follow.
What if all clients of the shop and sympathisers would leave a message of support in a public place front of it? Just like a recent road death, which (in France) leads to a small congregations of bouquets of flowers in the place where the victim died. It attracts the attention of passers-by, hopefully makes them think and serves to hearten the shop staff, so that it will still be there tomorrow, serving the hobby.