I question the sanity of the above question.
Regardless of which possible interpretation, both are just unfathomably bad ideas.
1) There are laws against reusing discarded mattresses, and for damn good reasons. Asking if the mattress was any good is just dangerously dumb.
2) While I get that LSD is an illicit substance, which most people* would only obtain through dodgy means, this by no means suggests that "I got it from a discarded mattress" is a suitable route of appropriation. As such, asking if the LSD was any good is likewise, just dangerously dumb.
*(LSD, or at least similarly bio-active compounds, can be obtained far more safely and reliably if you have the necessary knowledge. Such as knowing that Ergine, a biologically analogous compound with similar bioactivity, is found in a large number of botanicals, a handful of which in sufficient quantities to produce useful highs. This removes the dodgy dealer from the mix entirely. If you are just looking for wild hallucinations, there's always psilocybe mushrooms (which are easily grown in an aquarium on coffee grounds), and ergot fungus, which grows on rye berries. If you are willing to risk it, there's also jimsonweed, which grows wild in roadside ditches. The use of an entheogen/hallucinogen is an inherently risky activity, and is not advised, because it will probably never be safe. Regardless, 'safety' is a spectrum, and "Getting the stuff from a discarded mattress" is pretty damn far on the "Extremely risky" side of the spectrum, while "I grew it in my back yard, and took it knowing dosage would be all over the damn place" is just in the "Really not the brightest idea ever" part of the spectrum. "I got pharmaceutical grade ergine/lysergic acid from a pharmacy, and I properly measure my dosage" being the "Least risky." )