I'd start with a call to the Sheridan regional office, 307-672-7418. They may have someone or will put him in touch with the district game warden. Also worth a visit to the Gillette Visitors Center 1810S Douglas Highway Suite A, or by calling (307) 686-0040 - however a visit is more likely to produce than a phone call. If all else fails, drive the creek bottom roads in those hunt areas and look for irrigated hay fields and/or stored hay crops, knock on the door and ask permission. It is helpful to let them know you did have prior permission with XXX, but that they changed their mind.
I don't know if there was a severe die-off due to EHD/bluetongue this summer, but if so it will be really hard to get access in areas that were hit hard.