Hi there! Sorry that you're sad, but I can definitely help here.
We store campaign and response data in your account for 18 months; your data is archived after that time period. We recommend saving your mailing's webview and/or response as a PDF so you can easily access it at a later date, and you can find those steps in this Resource Center article.
If one of your campaigns was sent within the 18 month timeframe, just send me one of those links and I can take a deeper look here!