flagged e-mails "disappear" when that e-mail is pushed off the initial inbox screen

You can flag e-mails from any provider in the mail app in ios6. The e-mail then appears in a "smart" folder called "flagged" under the "VIP" folder.

If you flag a e-mail for future reference and that e-mail gets pushed down the inital inbox screen (when you have to touch "load more messages on the server" to see it) your flagged e-mail will disappear from the "flagged" smart folder until you load it again by touching "load more messages...".

This kind of behavior limits the usefulness of flagging e-mails. flagged e-mails should be cached on your phone always until you un-flag them.