@xxKatwhixx, I'm so sorry to hear about your dad. I'm glad you sought medical help and hope that you get more information quickly. None of us like having our PWDs (persons with dementia) in hospital but sometimes you need the care.
Some very good advice above. To emphasize a few points:
Definitely contact the PALS team.
Tell everyone loud and often that he had a failed discharge, and you don't want another one.
Refuse for him to be discharged home. Get a discharge to an assessment bed, a rehabilitation facility, a respite bed, anywhere but home. You need information, an OT assessment of the house, and necessary supplies and equipment at the house. You need continence supplies. You likely need a carer package. You need the carers assessment for your mother and the needs assessment for your father. You get the idea.
Don't let them fob you off! Advocate not only for your father's medical needs, but also your mum's needs as a carer.
Hospital stays can be very stressful. I am sorry about this difficult and tiring situation and wish you all the best. When you have the time and energy and if you are so inclined, please keep us posted. Best wishes.