Your reasoning is correct. If you don't like this solution that isn't orthodox, you can try to reinstall flash from entropy, if you have installed sabayon at least from precedent version of flash player and you have active sabayon-weekly repositories. In fact sabayon-weekly allows you to downdgrade packages if is it present in his cache. For the next times I suggest you to activate sabayon-weekly. Alternatively you can downgrade your packages from portage, but ,in this case, you have to advise by an expert, not me!!.