I want see an ad that YouTube showed me days ago. Can I do that? How?
The most obvious answer for this would be "there is no element for this in any UI, so this isn't possible".
However: We know that Google stores previous interactions with ads. And thanks to privacy laws, Google is required to tell what data it stores about us. Now, there isn't any element regarding this on Google Takeout, but you can use this contact form (or, once GDPR in in practice, contact their data protection officer) to get the data.