The fishing line story (and the conspiracy theory spun from it) is not supported by the evidence we have available about Thomson's corpse.
That no 1917 account makes any mention of suspicious fishing line is important. Clearly, in 1917, either no fishing line was observed, or if it was observed, it was not regarded as in any way important to Thomson’s disappearance and death.
Why Robinson would wait thirteen years to offer this insight, particularly if he felt it provided evidence that Thomson might have died by foul play, is difficult to understand. Making Robinson’s testimony even more suspect, in the early 1950s, he added details to his story about the fishing line. Robinson stated that when he examined Thomson’s corpse, he found the line was “carefully” wound “16 or 17 times” around Thomson’s ankle. Robinson noted that he could prove this claim because he recorded his observations in his diary. We know, however, that his diary says nothing of the sort; it doesn’t mention fishing line at all!
Robinson’s ‘fishing line’ stories from the 1930s and 1950s do not agree with any 1917 evidence (even evidence recorded by Robinson himself in 1917). This should raise our suspicions about the tale. That Robinson’s accounts gained new elements and more details over decades also suggests skepticism about Robinson's claims – particularly those furthest from the experiences he describes - is necessary.
Perplexed? Challenged? Interested in reading more?
To read more evidence about Tom Thomson's death, and to learn how story-telling about Thomson's death has diverged further and further from the evidence, read The Many Deaths of Tom Thomson: Separating Fact from Fiction (Dundurn Press, 2016).