One, I wasn't driving the vehicle based on 3 witness testimony
Arrest only takes probable cause. Just because you are (possibly) not guilty does not make the arrest "bogus" (or otherwise improper). Having people say you didn't do it when they found you in the driver's seat isn't going to be overwhelming. In fact, it many cases the fact that you are behind the wheel is presumption that you are operating the vehicle and if you are intoxicated, that's not only enough to arrest you, IT IS ENOUGH TO CONVICT YOU.
I had a significant head injury which caused me to lose my memory so I can't say I was given my rights, processed, or arraigned as I have no paperwork of the arrest, because of my head injury and subsequent memory loss. I was in no condition legally to consent to a blood tox. None of these things raise a red flag for you?
It makes a giant red flag that there is probable cause that you DID commit a crime. Finding people who are drunk or otherwise intoxicated who can't remember how they got there is far from uncommon.
Understand there's no obligation for you to be "given your rights." Miranda only applies to questioning once you are taken into custody. Any interaction between you and the police prior to being placed in custody needs no such warning. It sounds likely they didn't do any such questioning. Furhter, Pennsylvania's implied consent law means you've agreed by getting your license to getting tested when you are arrested for drunk driving. NO warning need be given to you prior to this testing. The only warning required in Pennsylvana is if you try to refuse, the officer is required to tell you that you'll lose your license if you refuse.
Unless they hold you in jail, there's no requirement for an immediate arraignment. In fact, they don't have to even do much at that point. Typically, you'll go up before the duty magistrate and issue you a bunch of papers. This will include an order to return to for your preliminary hearing/preliminary arraignment. If you haven't yet been mug shot and fingerprinted, that will happen then. A formal bail will be set (most likely ROR again or on your own recognizance). The DA will provide evidence that there was probable cause for the arrest and once that is done you will be set for the real arraignment in common pleas.
It would behoove you to have a lawyer. It is not a slam dunk. Furhter any immediately challenges and/or plea bargainly is usually done just prior or at the preliminary hearing. It would well behoove you to have an attorney BEFORE THEN for your best cases.
This is far from a slam dunk despite what you thnk (and why you think any of this given the fact you admit you can't remember is beyond me). The lawyer will look independently at the witnesses in a dispasionate and legally expert manner as to wheher the stop was valid (since you were already parked, it's a consensual stop and the cops are free to ask you questions), there was probable cause for the arrest, what the evidence and observations that support the charge were, etc...