If Box 15 shows IN and there's an amount in Box 17, they withheld IN taxes.
You prepare a non-resident Indiana tax return and on your W-2 delete the amount you entered for Indiana income. Leave the withholding amount in there.
You want your Indiana return to show $0 of Indiana income. That will get you a refund of all your Indiana withholding.
Your Ohio return is a regular full-year resident tax return. Ohio will tax you on all your income as an Ohio resident.
