The Idaho tax website is specific with regard to compensation (income reported on a W-2 is compensation):
"Work only outside Idaho during the year: You have no Idaho compensation."
Idaho Source Income | Idaho State Tax Commission
The bonus is definitely taxable by Ohio, since you received it while a resident of Ohio. It seems to me that it is not taxable by Idaho, since by Idaho's own criteria it is not Idaho compensation. I think this would particularly be true if no Idaho taxes were withheld on the W-2 that reported the compensation.
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
