I have searched in Google and I can't find anything about any earmarks going to Ohio. I am probably missing something but do you remember where you read about this?
I've got some oceanfront property in Florida and a bridge in New York I could sell you real cheap. 
Just an educated guess based on everything that's going on. Public meetings about US 23 just out of the blue last fall, this 75-15 vote that we need i-73 and that newspaper opinion piece that this is the wrong way to use earmarks and what gives earmarks a bad name. That newspaper piece was written in another state, but with everything else going on, I'm betting that money is earmarked.
https://www.appropriations.senate.gov/congressionally-directed-spending-requests-chart
Just the requests, not the final decisions.
According to the spending requests, Senator Graham of South Carolina has requested $15 million to "complete right-of-way acquisition" for the I-73 corridor in Horry County.
As for I-73/I-74 in Ohio, there were no requests listed. Bear in mind the above referenced chart pertains to Senator requests only, not House members. However, until the I-73/I-74 extension is officially designated a project by ODOT, it's unlikely any "congressionally directed spending" will be requested, even if only for a study.
Right now, and let's be realistic, extending I-73/I-74 in Ohio is just an idea, a line drawn on a map. There's a long way to go, and many steps to hurdle over, before this becomes a reality. On a positive note, there appears to be considerable enthusiasm and political support for the project.