Clay bars are not abrasive, they're more of an adhesive. They work by grabbing particles from your paint.
With that being said, try some Zymol HD Cleanse in that area. Use moderate to heavy pressure in straight lines. You want to see the metal of your hood actually bow in a little. You might have to do it 5 or 6 times to pull that etch out of there, but it should work if it's true that it was only on there for a short time. It'd probably be a good idea to HD cleanse the entire hood. If you don't, you'll have a deep, slick, clean spot and the rest of the hood will look bad.
If you can't pull it with the HD Cleanse, the only other option is to wetsand/polish.