Presuming you still have the e-mail with the attachment, or remember the file name of the attachment, open Cortana and type the control prefix, files: and follow it immediately by part (up to all) of the file name. You should find it in the search results.
I can't tell you where you saved it, but I can tell you how to find it.
Brian - Windows 10 Home, 64-Bit, Version 1803, Build 17134
A great deal of intelligence can be invested in ignorance when the need for illusion is deep.
~ Saul Bellow, To Jerusalem and Back