How does the hard drive on my computer become the fruit of someone else's labor if I use it to copy information that doesn't deprive them of the physical media on which the pattern is originally stored?
Because they didn't create the physical media, they created the IP
Doesn't the act of copying require one to expend accumulated capital/do work?
That's irrelevant to the issue at hand. The copies are not valuable because of the medium they're in, the copies are valuable because of the original IP.
How could a pattern exist absent a physical media?
It doesn't have to.
How could someone own something that doesn't tangibly exist in the physical world?
It's called intellectual property. That's how. All ownership is an abstract construction, so your physicalist argument is irrelevant.