"Depleted" in this case would just mean mined, transported, and made into something. It doesn't seem farfetched to imagine that, say, an electronics factory would be reduced to an easily accessible deposit of copper or gold in a few million years.
It depends how long the civilization is around. A lot of metal could end up impractical to mine. You can recycle metals, but little chips are being lost to wear and corrosion over time. We're slowly spreading small amounts everywhere.
Some of that would be theoretically be recoverable with a lot of effort and energy, but some of it will basically be gone. No one is going to get back small bits of metal fallen off ships into the deep ocean.
