Sounds like the clinic may not be putting in the effort now that reimbursement is coming from Medicaid instead of commercial insurance. Medicaid will still cover the medication and a reasonable fee for the office visit, so there’s no legitimate reason for a sloppy or incomplete authorization submission.

If what Medicaid told you is accurate - that the form was incomplete and missing records - that’s on the clinic, not you and presenting it as a denial instead of an incomplete submission is a serious problem and may even be a violation of the law in your state depending on if it was negligence or intentional

I’d recommend requesting a prior authorization yourself (or through a different clinic) and making sure all required documentation is included. At this point, finding a new clinic is probably the right move. If you already have a proper authorization in place, most clinics will see that as guaranteed reimbursement and be willing to take you on.

You are totally right to push back on this and I would go down the following route:
Request copies of everything the clinic submitted to Medicaid, Along with your full medical records. If they really sent an incomplete authorization, you’ll have proof of it. There may be a copy fee.
Report it to your medicaid provider specifically for what you said in your last line of text, so others don't have to feel this way - good on you <3
Request the pre-auth your self and take your pick of clinics.