Final answer:
The author is foreshadowing a significant plot development related to the missing boot, which, though trivial now, will prove important later.
Step-by-step explanation:
The author is most likely foreshadowing a significant event or revelation tied to the missing boot in the passage. Sherlock Holmes hints at the importance of the seemingly trivial detail, suggesting that while the incident may appear foolish, it is likely that the boot will prove to be of consequence later in the story. This attention to a minor detail is a common literary technique used by authors to set up future plot developments that may initially seem inconsequential but are actually pivotal to the narrative.