Maybe they had hens with them. From my experience, they often quiet down as soon as the hens arrive. Then they go into strutting behavior. Did you try sticking around a while? Sometimes they will start gobbling again (crow calls, geese). Also try sneaking very quietly and carefully towards the last gobble. Keep your eyes peeled (use binoculars--watch out for other hunters) --maybe you will find " them" with their hens---then go to work on calling the hens the toms will definitely follow!