This makes me shudder. Such a functionality would mean that they stored your failed request in some sort of database, a database that they later used to send you a personalized marketing email. A machine cataloging our voice for later inspection is a very dark future. Alexa should delete and scrub any iota of voice that it doesn't instantly understand.
"Oh, remember last week when I though you were asking me to buy you a pot plant? I now realize you were asking me to buy you some pot from Canada. It will be arriving in two days."
"I didn't understand it at the time, but I now realize that you were yelling at your husband Alex, not Alexa. Your social credit score has been adjusted to reflect this negative interaction."