she heard you coming and bolted! That's mom trying to do a decoy away from her babies, not abandon them! She must've gone nuts when she came back and found them gone! Are you going to look for her? Her milk will give them naturally immunity to so MANY viruses! As on other threads going right now, see recommendations for trapping. But she may be friendly if you could find her. Start by putting out food? I dunno. I don't grasp really how far you would have to go to find her, i.e., where this property is....?