Tru here.  

My personal short-term VISUAL understanding is much much better than my VERBAL understanding (for words), so …

When I ask the same question multiple times,
then my husband makes the answer into a picture, and
puts that picture on my workdesk
so that every time I get distracted and look up … I see the answer.

In your case,
My husband probably would have made a “shopping list” on 3×5 card — with “curtains” in big letters with a DRAWING (because when scattered i understand pictures much better than words).
He would have asked me to hold the shopping list until we get to the store.
That would put the picture in front of me every time i thought of asking. (However, he would also add a couple other things like maybe “hooks” on the list so that it actually looked like a “real” list, so that i did not feel patronized).
He is creative like that ((smile))  

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General Communication Tips: 

a) My personal verbal short-term memory is severely impaired so don’t expect me to remember ANYTHING that you tell me (even for five minutes)!
b) Use shorter sentences than usual; with less extra phrases I am more likely to remember the subject, object, and verb in order to connect the sentence.  I am NOT stupid; I understand each word individually, but have difficulty connecting them as concepts.
c) Minimize descriptive monologues or conditional clauses.  (I may get the “if” part, but by the time you get to the “then” part I have lost the “if” entirely.)
d) Please wait short pause after each sentence for me to “compute” your words, then you can resume speaking for the next sentence.  The time necessary between sentences may change from day to day or even moment-to-moment (especially true with Lewy Body Dementia).

g) Really I am not purposely developing dementia in order to grow your “patience quotient” — it is just a side-benefit for all concerned.  ((big smile)) …  And the coup-de-gras; please allow me to interrupt if I raise my hand, because otherwise the thought will be forever lost.

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If I ask you the same question multiple times there is a good chance that for some reason the answer did not “register”. 
This may be because your answer did not address whatever concern caused the question to start with. 
You need to be a detective; look for something that maybe you did NOT answer earlier.  An example might be if the question is a matter of calendaring then maybe my concern is another event I think may conflict with this, and it might be helpful to visually compare the events on calendar.  … or i might be worried about something that is to occur during this scheduled event (doctor appointment).

If I asked a question and your answer was “I don’t know”,
then I can almost guarantee I will not remember your answer
so I suggest you just write it down now, BEFORE I ask you five times. 
LOL to my husband! 
How could you (the awesome answer man) NOT know the answer??  
— Of course that does not compute!!

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