My mom (95.5) is having problems with short-term memory loss and it seems to have happened too fast. Checking for UTI. Anyone else seen this?

If its Dementia there may have been signs you just didn't see them at the time. Found this when looking back. UTI usually doesn't have memory loss. Usually hallucinations, being agitated and hitting. A small stroke could cause memory loss like this. Dehydration, if she is diabetic, low potassium. I would make sure she gets a full workup.