No - past chapters establish that there was a delay of a year and a half between the "wreck" of the Ares and pronouncing Rachel dead - which was around Christmas time seven years before the story. The statute of limitations was tied to seven years after she was declared dead - so if there was insurance money, Dirk would have gotten it at that point.
I don't think that Rachel found the stash prior to the "wreck" - but she may have in the time since, or once Trevor is in Austrailia and reunited, he may try to create a similar stash place on the Ares and find that someone had beat him to it... Reason I don't think Rachel knew about the stash is that Dirk would have been much more paranoid about Bridget, and when he learned that part of the investigation was regarding Bridget and her husband, he would have agreed to meet with the police, in case not doing so might endanger Trevor.
DAMN - re-reading the prologue, two phrases jump out that I hadn't really paid attention to before...