He went to the bank today to have them evaluate the trade in costs. He had the information in the car and walked into the bank without it and got the wrong info. He may be on the phone asking about an administrative concern and accepts any answer, without thinking about how the answer may or may not answer the question.
I sent him out on two errands today, and he succeeded with both.
I read the full write-up from my husband's neuropsych evaluation, and they described a number of faults in his reasoning process that surprised me, even though I was aware of his dementia.
This situation is due to the illness. Sometimes he will remember, but often he won't. Try to get him into the habit of calling you when he is unsure, or can't find something. I have started to alert people he deals with about his condition, and tell them to call me if there is any question.
He will be worse in unfamiliar settings and when he is tired or sick.
I suspect I'm 6 months or a year ahead of you.
Make sure you have all your legal documents, medical, AMD, DPOA in order while you are both in good health and mentally competent.
As far as your question, you may have to discretely phone the person back with correct info for more accurate trade in value. You can explain your husbands situation or just say he didn't have all the info in front of him.
You have a long road so I hope you and hubby have support and patience for this journey.