Deleted emails don't usually go directly to email oblivion, they usually spend a few days in your mail account's "Trash" folder. Have you tried looking there? Or have you tried signing on to your email account using a browser, the emails could be in either an inbox or trash folder.

If your email system settings don't provide a cooling off period in Trash (for just this reason), it may be something that can be changed.

What email system do you use? How old is your iPhone?

I think it's just for this reason that "they" recommend using IMAP rather than POP for e-mail on a mobile device.

I have searched every possible folder, to no avail. My trash-y emails :) hang around for about a week, which is the way I want it. This has happened 3-4 times over the last 6 months, so not often. Lindsey, I'll look into what IMAP means--I saw this mentioned when I googled the problem, but didn't really understand the possible answers.

Thanks for the replies.

You didn't answer my question about trying with a browser, but how about this -

Are you using an app on your phone for the email? If it's the native app, try removing the email setting and then signing up again. If it's a single purpose app - the specific Gmail or Yahoo mail apps for example, try uninstalling it and then downloading and installing it again. Delete any cache entries first.

I thought pop and imap were for web access from another email provider. My smartphone apps just log in using user name and password, no other entries or choices are required.

http://www.howtogeek.com/99423/email-whats-the-difference-in-pop3-imap-and-exchange/