Lost emails?

I have to show a certain email which I can find again. It's about the fact that I have to show an email about a purchase in the playstation store. I received it a day or two ago, but I can't find it again. Can anyone tell me how to find emails that can no longer be found? I've already searched everything, etc. Or can anyone tell me how I can see completely deleted emails again?

If an e-mail is irrevocably deleted, then it is irrevocably deleted…
That's what the name says: irrevocable
Ben