How I wish this wasn't happening. If it's any comfort to you, my Boo ran out the door after another cat in the dead of winter, well below zero temperatures and I too fell on the ice and got a goose egg on my knee, just like you did. My son was home for the holidays and we searched for him day and night. He had never been out of the house since I took him in ane he being coal black, we thought we'd easily see him against the white snow. Wrong. That night at exactly midnight, snow coming down by the pound, I was a crying mess, sure that he'd run off and I was lying in bed w/the TV on low volume when I heard a cry outside. I had left the garage door up a few inches so that if he did come back home, he could go into the garage. I ran to the inside door and there he was, sitting on the steps crying. Covered w/mud but safe. Let's affirm that the same thing will happen w/you and Willow.

Blessings,
Mary