Gas Rights Only

I am attempting to purchase a property with a house and acreage. The man I am trying to buy the property from sold an adjacent parcel and thought he retained the oil, gas and mineral rights and was including these in the sale to me as well. However, in the deed that the buyers attorney prepared when he sold the property says only “the seller excepts and reserves the gas rights”. There is a lease on the property that mentions Oil, Gas, Coal Bed Methane, Liquid Hydrocarbons but there has been no development. Gas is far and away the valuable commodity as there is the potential for shale gas in the area. However, some of these wells produce oil. He said it was understood when he sold this parcel that he was to keep the mineral rights including the oil and gas and figured he could just go to the new owner (who is supposedly a friend) and get this changed. However, when he approached them to correct this error they said NO! Am I stuck? I am new to this and posted a blog on this topic as well.