How long does it take for Aunt Polly and Becky’s mother to worry about their absence? Why does it take so long?

Mrs. Thatcher and Aunt Polly don't realize that the children are missing until church the next morning. They both assumed the children had stayed overnite at a friends house.

“Is my Becky going to sleep all day? I just expected she would be tired to death.”
“Your Becky?”
“Yes,” with a startled look—“didn’t she stay with you last night?”

“Why, no.”
Mrs. Thatcher turned pale, and sank into a pew, just as Aunt Polly, talking briskly with a friend, passed by. Aunt Polly said:
“Goodmorning, Mrs. Thatcher. Goodmorning, Mrs. Harper. I’ve got a boy that’s turned up missing. I reckon my Tom stayed at your house last night—one of you. And now he’s afraid to come to church. I’ve got to settle with him.”
Mrs. Thatcher shook her head feebly and turned paler than ever.
“He didn’t stay with us,” said Mrs. Harper, beginning to look uneasy. A marked anxiety came into Aunt Polly’s face.