The process of fossilization by definition replaces organic material with very hard minerals. The fossils we find today are the ones that by chance have fossilized into the hardest minerals under the best conditions for preservation -- buried in the right kind of mud at the time, or by tar more recently, or in ice, or in a bed of limestone.
I can find one not-great reference suggesting that carbon fiber items are expected to be in landfills for on the order of hundreds of years -- not very long in geological scales. Steel rusts and degrades spectacularly easy, and a lot of the steel we've produced is exposed to conditions helping it along.
Neither of these items is susceptible to the process of fossilization; it's that process that helps preserve some things for a long time. The stuff we make has to last that long all by itself, and we're not that good at making things yet.
