There are no 'mistakes' in IFM - most of the continuity problems are due to the author doing things at the behest of the publishers who changed their minds after the fact. Despite events already being referenced elsewhere, the decision was then made to ignore them.
It could (and should) have all been retconned fairly easily had they wanted to. There would have been no issue.
I find the decision baffling but there's nothing you can't retcon yourself.
It would be nice if the fate of a major character was addressed at some point though, even obliquely...