Sleep and medicaid issue?

Ok, my doctor prescribed me Lunesta to sleep from insomnia, well anyways, all this special paperwork had to be done to get this drug with medicaid on my docotrs end and pharmacy and medicaid. To make a long story short, I have been waiting a week and my doctor still hadn't sent his end of paperwork in, so I had pharmacy refax it to him to remind him or his staff, well the pharmacy called me later on and said the doctor didn't approve of the Lunesta, but I could still buy it with his prescription, or have him change it to ambien or resteral. Does anyone have any clue why he would do that? Does it make any sense, was it just too much paperwork, or was medicaid more apt not to pay for lunesta? Because aren't lunesta and ambien somewhat similiar? Someone let me know what you think. I'm so confused, and I'm wondering if the ambien will need this prior authorization also, and if I'm gonna have to wait a month or two to get it. I'm so frustrated with my doctor's office, they do not do their jobs! Someone let me know what you think.