Is Superstring Theory fundamentally flawed? I suspect that i'm missing some fundamental concept here, so please kindly help me figure it out (if any).
Suppose that superstring theory is a valid theory of nature. That is, every fundamental particle of nature, say $p$, is a vibrating string, with each vibrational mode corresponding to a different particle. Define $\Lambda$ to be the highest energy currently accessible at particle colliders and $p$ to be some fundamental particle that can only be experimentally detected at energies $>\Lambda$. Note that $p$ occurs with its supersymmetric (susy) partner, say $p^*$. Consider the vibrational mode of the string that corresponds to the particle $q$ that has exactly the same properties as $p$, except for the mass. More precisely, the mass of $q$ is sufficiently small such that $q$ can be experimentally detected at energies $\leq \Lambda$.  Note that by supersymmetry, $q$ should also occur with its susy partner, say $q^*$. Observe that we now have a pair of susy particles $(q, q^*)$ that can be experimentally detected at energies $\leq \Lambda$. But we know that supersymmetry cannot be detected at energies currently accessible at particle accelerators, which is a contradiction ?
 A: The question contains a peculiar argument along the lines "if there exists a pair of superpartners with the same mass at above experimental energies, then there must exist such a pair within experimental energies". I don't see what the exact reasoning is, but it is probably based on some misconception about how mass works in string theory. 
In the standard model of elementary particles - which is what string theory has to reproduce in order to match reality - most particles are massless until the Higgs gets involved. It is the same in string theory. For example, quarks, electrons, and neutrinos all correspond to massless states of the string, which then acquire mass through interaction with a stringy counterpart of the Higgs mechanism. The higher vibratory modes of these string states are superheavy and not relevant to observable physics. 
With respect to supersymmetry... If supersymmetry is unbroken, then yes, every state should have a superpartner of the same mass. But supersymmetry can be broken in many ways, and there are also string theory "vacua" which are not directly supersymmetric in the first place. 
