The owner never got a brand inspection (heck he did not even believe in a vet unless it was bleeding -_-') so can I still obtain one? I never knew you needed a brand inspection. I don't know if my friend's horses have them for their horses 0.0
In my experience with brand states, I think they have done a poor job in getting the information out to non large producing livestock owners. Cattle and dairy producers deal with them just about on a weekly basis so they know and understand the laws backwards and forwards but the parent who buys 2 horses for the kids doesn't get the same information unless the seller is knowledgeable in the states brand laws as well. The internet give us access to the information but if you don't know what you need to be looking for all that information doesn't do you much good.
Start with the old owner. If you can't get anywhere with him than call the BI for your county and get advise from him on how to proceed. The state of AZ does not want your horse nor can they afford to feed her so they are going to work with you and get things ironed out. Dig up old vet records that show length of ownership, registration papers... anything that creates a paper trail.