Reading this reminds me of the boy who cried wolf. People don't believe in him because he has a bad record of lying, and so does David—who was also known to his parents and sister for his absentmindedness. Like the villagers who doubted the boy's honesty, his family also doubted David's presence of mind because of his not-so-reliable behavior. I'm sure his sister was upset about her mistake, but I think David is more upset because he now knows that even his family doesn't trust his words.
Thanks for sharing @supernova004! Good day!