You may wind up being a dog wrangler and community sleuth

The Story:  Here I am, minding my own business, womanning the desk on a slow weekday morning, when a golden bundle of fur streaks across the library, heading straight for the preschool play area.  Up I jump in a flash and I find the dog sniffing and briskly walking through the area.  It goes up to a couple of people but then quickly turns away, as if they're not what it's looking for.  I slowly approach it once it stops for a minute, but then it bolts across to the other side of the children's room.  It slows down and walks down an aisle of non-fiction towards me, and I crouch low and try to coax it towards me.  It comes up to me, sniffs me, and sits down.  I see it's got a collar with several tags, and then it's fairly easy to grab it by the collar and walk with it into the administrator's office, which happens to be one of the only rooms with a closable door.

Myself and my two bosses start chasing down leads, while the dog sits herself on the floor and calmly enjoys being pet while we read off tag information.  Her name, apparently, is Grace Louise.  One of the tags leads to a phone that is out of service.  The next one is an online lost pet service, and eventually leads to a shelter in the South that adopted the dog to its owner up here in New England, and they have the same old phone number as we do.  They reveal, however, that the dog was well-cared-for down there until its owner died and it was surrendered to their shelter before being fostered then adopted up north.  The third tag leads to a local vet, who tells us that the owner up here is deceased, and they don't know who is currently caring for the dog.  We get the former owner's name from the vet and call the police to see if they know who next-of-kin is and if they might be able to track down the dog's new caretaker.  We then realize that this is the exact same dog that ran through the library a few months ago with its now-deceased owner on its heels after she had gotten loose during a walk.  This dog got loose and came to the library several times over the years, according to my coworkers, who took turns coming in to the office to pet the dog while we worked on finding its caretaker, though this was the first time it happened on my watch with this particular dog.

The owner's death was a well-known incident in town, as it was a fatal hit-and-run that people were still talking about in its own right.  We go on facebook, of all places, on a well-trafficked community forum on there, and find out who is caring for the animals from comments on the thread about the crash.  Then animal control comes and gets Grace Louise and confirms that they also believe they know who is taking care of her, and it is the neighbor we identified from the forums.  So, off they go to reunite this poor, sweet dog with owner #3.  The shelter down south offered to take the dog back to one of its northern partner shelters and foster it/find it a new home, if we did not locate the owners or it didn't work out for whatever reason.  Hopefully, that won't be necessary.

The Lesson:  Keep up with local news.  Though print newspapers are slowly dying, town papers and related websites are still heavily read in most places; it doesn't matter if you are in a big city or small town.  People still want to know what's going on around them, and they will often flock to online forums to talk about it as well.  As soon as we got a name, we recognized it from the headlines, and knew we needed to adjust our approach.  Even if you don't live in the same town as you work in, take some time to at least skim the newspaper.  Fifteen minutes or so a week of reading on the clock is perfectly justifiable professional development, because you never know when community connections will come in handy.

Learn how to behave around stray/lost/frightened animals.  I read up later about how to catch a skittish dog, and while some of it may make you look and feel foolish, there are some basic principles there that make sense.  When I was running at the dog, it also ran.  When I stopped moving and crouched, I was no longer a threat, and it approached me.  This particular dog was very social and seemed to think the running was a game rather than fleeing in fear of me, but still.  Me changing my behavior cued the dog to change hers.  Obviously every situation is different, but it helps to be able to get a dog to come to you.  A dog will pretty much always be able to outrun you; they've got twice as many legs, and have a very low likelihood of wearing movement-restricting clothing.

Expect the unexpected.  This particular instance happened in a public library setting, but I have seen dogs running amuck in university libraries too, albeit less frequently.  Any place with automatic doors has the potential for animals to let themselves in.

Resources:
Local newspaper
Facebook/local online forum
Pet tags and pet-location services, such as 24PetWatch
How to behave around lost pets
How to catch a stray dog