Why was the old man walking in the train?Because he was looking for______.

It was a weekend in summer and all the town trains were crowded．An old man was walking in the train，looking for an empty seat．Suddenly he saw one and got in．A small bag was lying on the seat and a well-dressed gentleman was sitting beside it．
    "Is this seat empty? "asked the old man．
    "No．it is occupied by a man who has gone to buy a newspaper．He’ll be back soon．"
    "Well"，said the old man，"I’ll sit here until he gets back．"Ten minutes passed．The train started． "He has missed the train．"said the old man, "but let him not lose his bag．"With these words he took the bag and was about to throw it out of the window．The well-dressed gentleman jumped up and cried out，“Don’t ! It’s my bag!”