Home Forums Networks & Cross-Platform Networking Mail, reply and attachment they sent if destroyed

Weird one, if no one knows, I'll call Apple.
Frequently someone send me a pdf or some or a work or some type of attachment. The attachment if good, it works, it has an icon; you can drag it to the desktop. But when I reply to the email --then it's inexplicably gone/ destroyed. All I see is a text remnant of it... ie shoes.pdf, but no real pdf can drag on desktop anymore.