What to do when the owner doesn't pick up on time?

For some reason your question didn't appear on the board in a timely manner.

However, looking at the calendar, the information you provided, and the dates involved, your client paid for her dog to stay with you until Monday evening. She dropped the dog off on Thursday evening and, I assume, paid for 4 "nights." Each "night" of care is good for up to 24 hours. Therefore, you were paid if she picked up the dog anytime prior to Monday evening.