Lost Cat Situation

This is something new I decided to post.  This experience actually happened to me.  Back in the summer, a storm knocked out our power.  Because the house was being worked on, guys were moving all over the place.  I stayed somewhere else.  One of the people working left a window open overnight and one of our cats got out.  We didn't notice until the next day.  Before I tell you what we did, I'd like to know what you all would do in that situation.  Please let me know.