Test Rocket!

Personnel at a rocket testing station recover an unfamiliar but mechanically identical large rocket that had travelled from space and landed; when dismantled it yields a living humanlike being who breathes and eats but does not comprehend written instruments or the technology, appearing uninterested in the craft. Investigation reveals unfamiliar materials and returned domestic instruments, leading staff to realize the craft was a test vehicle built to their design. The story closes on the unsettling suggestion that the launch was an experiment conducted by others who replicate and test unfamiliar species, reversing the observers' assumed superiority.