Mouse droppings are often thought of as the "most obvious" sign of mouse infestation in a home. While that point can't be argued (after all, if they're dropping in your home, they're obviously eating and living inside as well), the connection between their location and the location of the mice in your home is much more nebulous. In fact, it's safe to say the connection is very dim.
You see, mice are a lot like humans, pigs, or cats: they never "go" where they eat or live. They tend to create a specific area of their living area as "toilet" or simply go to the bathroom far away from their home. In the outdoors, that means they tend to go on the ground outside of the burrow.
In your home, that means they are just as likely to find a random spot to drop their load. Their instinct towards staying clean and free of their own filth is your worst enemy when it comes to locating their home: there's a stronger chance of you accidentally finding it than there is of your finding it when using mouse droppings as an indicator.
If you can't rely on the old "mouse poop" method of DIY infestation diagnosis, what can you rely on? Not much. Instead of trying to take care of the problem yourself, call a professional today. They can help you figure out where the mice are in your home and create a control solution that will get your house mouse-free as soon as possible.