  We analyze the recently proposed "pattern-matching" phase of a Gaussian
random heteropolymer adsorbed on a disordered substrate [S. Srebnik, A.K.
Chakraborty and E.I. Shakhnovich, Phys. Rev. Lett. 77, 3157 (1996)]. By mapping
the problem to that of a directed homopolymer in higher-dimensional random
media, we show that the pattern-matching phase is asymptotically weakly
unstable, and the large scale properties of the system are given by that of an
adsorbed homopolymer.
