Yes, there exists a store of "natural rights". The Bill, in enumerating some of these rights, is not legitimizing those enumerated against those not so, but rather, utilizing those few specifically enumerated as a check on the scope of government power, for which task some of those not enumerated may prove themselves of utility at a later point, though which are in any case still afforded equal confidence, and in no way to be considered incidental to the basic purposes and resolution of the founders, who so hardly touched upon them in our judiciary character, but rights which may not be so dispensed with in the same. The 9th simply states this fact explicitly.
The right to jerk off is as much a right as anything else, but specifically enumerating it in the legal framework would not provide any meaningful and practicable check on the scope of federal authority, so there was no reason to bother with it. But the fact that it was not bothered with, is not an indication that it can be infringed upon, or is even any less of a right than the right to freedom of speech: this later right, contrarily, whose enumeration and precise legal definition were incredibly useful in articulating certain checks on the scope of governmental powers, was so included in the Bill for precisely this reason and this reason alone. This explication in the ninth, typifies the whole constitutional philosophy.
So people often read the whole Bill incorrectly. The Bill is not a list of rights the government is giving us, but rather, a list of checks on government power that we are giving the government, through the precise legal framework of those enumerations.
The idea of adding amendments thus boils down to the idea of enumerating, within this framework, extra rights from the common store in nature, which would be useful in further extending, or more perfectly articulating, that system of checks on the scope of powers between individuals, between individuals and government, and between the internal branches of the government itself, whose preservation it is the entire labor of the constitution to afford posterity. Only in this sense is the constitution a "living document," an idea no less generally misunderstood, as is the Bill of Rights.