I just cannot believe any Oncologist would set up a biopsy and not send the place doing it the MRI and Scan as a digital file. This is quick and easy to do! Next is why the hell didn't the biopsy place tell you a week ago to bring a disc of the MRI and scan with you, since they didn't have one from the doctor? This smells of either incompetence or outright just not caring, perhaps even stalling because you are on Medicare. Maybe they are seeing other patients that have better paying insurance.
Generally Oncologist have a direct connection to the labs and other doctors they use. If that was the case, then no reason the biopsy doc couldn't have looked up the MRI within minutes. I simply can't believe this has and is happening to you. If just one thing, that is understandable, but one major mistake or oversight after another, is unacceptable.
It sounds as though you need a cancer advocate to get this mess on track. You might check to see if your area has such. We have a retired Oncology nurse that volunteers to help any older patients get the right treatment and understand what the doctors are telling them. I would highly advise you find a knowledgeable advocate, before any more time is lost. Time is of the essence.
If the ER docs saw that T-12 had a tumor, then they did an MRI above the waist. T-12 is at the bottom of the rib cage, slightly above ones natural waist, and is where Thoracic meets the Lumbar. S-1 is above the tailbone and cancer there won't directly "eat up" the tailbone. The ER doctors had to assume that your cancer is metastasized and has spread to the Coccyx or tailbone, from S-1, and is destroying it. With that assumption, they should have had you to an Oncologist that should have ordered a PET scan and biopsy, immediately. That doc is the one responsible for getting all your info to the other testing doctors.
Call the American Cancer Society in Gainesville ... 800-227-2345 they can direct you to help and the support you need.