It isn't easy to answer a question not expected. So what I have done is go back the next time and ask them a followup. Like "I want to thank you for what you said about wanting what I have. No one has ever said that to me. I was tongue tied. Thank you so much.

Was there something else you had a question about that I might try to answer or clarify about what I said?"

This builds the other person's self esteem and also gives you a chance to say anything else needed.