Bear, I'm very sorry to hear about your dad. You must be very worried and stressed right now. No, I haven't experienced anything like this, but I am sure someone here has and I hope they will have some words of advice or experience for you.
I am also in the States and while I know things vary depending on what state/county/city you are in, I don't think it sounds like your father got the care he needed.
I would call his neurologist first thing tomorrow, if he has one, and his primary care doctor (whom I assume was informed of the hospital admission?) if he does not. They need to see him in their office ASAP to follow up on the new medications and advise you further. If he doesn't have a neurologist overseeing his care, or a geriatric specialist of some sort (but I'd strongly advise a neurologist who specialized in dementia), then you need a referral for an appointment ASAP.
You need to know more about the medications he has been given, for a start. I'm not a medical professional, so take this with a grain of salt and check with a doctor, but Exelon is a medication given for Alzheimer's type dementia, which is fine, if that's the type of dementia your dad has (as opposed to vascular, for example) and it's appropriate for him. The drug name is rivastigmine, for our UK readers. Seroquel (quetiapine) is an antipsychotic, although it's also used for other things. Antipsychotics do not always mix well with dementia patients and they should be carefully monitored, and they are not always the first drugs of choice. I do not want to alarm you, just make sure that someone who knows about dementia and medications is overseeing your dad's meds.
It sounds like he checked out okay medically, which is good, but also doesn't help to explain what might be going on (as opposed to if they'd found an infection which might explain his symptoms, not that I am wishing anything on your dad).
If he lives alone at home with no carers/services coming in, I am frankly surprised he was discharged to home at all. Remember that you can fight a discharge, should you find yourself in this situation again. You can seek help from the patient care/discharge coordinators, the geriatric social worker, the patient advocates, or even the chaplain if you can't reach anybody else.
A hospital stay can cause a sudden decline in functioning that can resolve, but I think you are right to be concerned.
You may not like my next suggestion, so brace yourself. If his neurologist and primary care doctor cannot help you, or he does not improve, then an option you might consider is to admit him to a Senior Behavioral Health Unit at whatever area hospital offers one. This is what used to be called, Geriatric Psychiatry, or Geri Psych. It is the US equivalent (more or less) of what is called in the UK, sectioning. It usually requires a minimum stay and the wards are locked. Sometimes this is the only way to get a person with dementia (PWD) the treatment they need, or to get their medications straightened out, in a setting where they can be monitored and kept safe, while also getting assessment, diagnosis, and treatment for any other medical conditions. It is not scary and awful like in the movies.
I am not saying, this is what your dad needs. I am telling you that it is an option and not to be afraid of it. I had about one minute to make a decision about sending my mother to the Geri Psych ward and it was very upsetting at the time. If I had known then, what I know now (that she would receive excellent care and the diagnosis she needed and a thorough assessment and a recommendation for an appropriate level of care and her medications straightened out, all with amazing nurses and staff), I would not have been so upset and overwhelmed in the moment.
I hope that your dad's incontinence and distress will resolve once he is out of the hospital, and that his physicians will be able to figure out appropriate medications for him and that you can ignore pretty much everything I wrote.
I am sorry if I have alarmed and upset you but I can sense you are very worried for your father and want what is best for him. It's always preferable to avoid the crisis, if you can, so I think you are smart to seek help and be proactive. This must feel so overwhelming for you.
I am sorry. Best wishes to you and your family.