How to filter/limit for syntactically invalid From: line?

I've been getting some spam recently with From: header lines like this:

From: aaaaa.org" <[email protected]>

Probably because of the unbalanced quoting, these show up in my mutt
index as being from "@" - just the @ character in the sender column.

What search expression can I use in / or l(imit) or similar commands,
to match messages with a From: header like this?  If I try to look for
any other contents of the From: header line, these messages don't match.
For example, if I do ~faaaaa or ~fno-reply I get _other_ messages that
have those strings in their From:, but not the message with the From:
line I showed above.  And of course ~f@ matches everything.

  -- Cos