Final answer:
Gilbert Dickinson went missing after a German poison gas attack during World War I, and there is no known grave for him. The exact reason for his death is not mentioned.
Step-by-step explanation:
Gilbert Dickinson, according to the Commonwealth War Graves Commission records, went missing between April 22 and April 24, 1915 after a German poison gas attack during World War I. There is no known grave for him. The exact reason for his death is not mentioned in the provided information.