Gold is soft but Amber is softer and we've found intact insects encased in that substance which are 230 million years old*. You wouldn't be likely to find a complete car or something in 60 million years but there will certainly be plenty of artifacts which were preserved through sheer luck. I wouldn't be surprised if most small manifactured objects would survive in archeologically recognizable form if they were accidentally lost in an anoxic environment. For example, imagine you lose your iPhone when out in a swamp. Drop a phone in something as thick as Pluff Mud, which is abiotic below the surface, and you've basically encased it in the exact kind of environment which has produces the best fossils we've yet found.