The Tenth Person's Reunion Dinner

On New Year's Eve, the male protagonist takes his newlywed wife back to his hometown for a reunion dinner. According to the rules in my hometown, red envelopes must be given to each junior before eating. The hero's father counted again and again, then suddenly dropped his chopsticks: "There are clearly ten people at the table, why did I only give nine red envelopes?" The whole family was stunned - there were clearly only nine people at the table, including the old and the young. What's even weirder is that no one can remember who the "extra person" is, but they can clearly describe that person's appearance: wearing a red cotton-padded jacket, bowing his head and not speaking, sitting on the seat closest to the door of the dining table. The hero's wife suddenly whispered: "Dad, is he suffering from Alzheimer's disease?" The male protagonist was about to explain when his phone suddenly vibrated and he received a text message from an unknown number: "Your dad is not sick. Look at the calluses on your mom's hands - she just dug out the tenth person's name under the table with her nails."