Just to play devils' advocate: I totally believe that we could identify any normal alloy, but what about more far-out kinds of materials? Humans have already e

Just to play devils' advocate: I totally believe that we could identify any normal alloy, but what about more far-out kinds of materials? Humans have already experimented with metamaterials, weird composites made of many different kinds of constituents layered or interposed in various ways, materials with embedded electronic or even "smart" computational capabilities, etc. Now imagine what a more advanced civilization might be capable of producing. I'm imagining a composite with embedded "smart" programmable behaviors that is 3d printed at the atomic scale. Every single atom is positioned intentionally to yield "smart matter" with incredible strength or other really exotic capabilities. I can imagine it being difficult to identify or characterize such a thing without destructive testing, and if we did have such a sample we'd probably be very reluctant to do that.