Question - Is there a term for a "forgotten attachment?"
Answer -
It seems like it happens all too often. The person who sent you an e-mail forgot to attach the document they said they are attaching. In fact, most of us have probably found ourselves clicking the "Send" button a bit prematurely at one time or another.
While I am not aware of any any official terms for forgotten attachments, here are a few options that came to mind:
mistachment
nontachment
untachment
vaporfile
d'oh! document