Sorry...no sympathy for you. If your email is that important it should not be trusted to web mail. Download-install-and learn to use a proper email client (e.g. ...Thunderbird) and configure it (POP3) so that your messages are downloaded to your hard drive. If that is not an option, then copy/paste whatever is important to you into a separate file.

Sorry about the problem, but I have to say that issues like this are what made me give up AOL many years ago and never look back.

As said, this is a first. So, never a reason to quit.

And I should add, I never heard any discussion re using only a "proper email client." Further, we novices need your guidance & help, not disdain for something we weren't aware of.

Even so, thanks for your comments.

Might look though your other folders. I lost all most current mail once, think I fell asleep with mail open and drag-n-dropped them somehow into another folder. Long time missing until I bumped into them & guesses what probably happened.

Yes, I did explore other folders. But no luck.

Fortunately, all email in personal folder appears to be intact.

E-mail was originally designed to be downloaded OFF the server and permanently-stored local on the user's computer. That's what a mail client program does via the POP3 (Post Office Protocol 3) protocol. Users wouldn't leave mail "permanently" on the server any more than postal mail would be left at the US Post Office. The e-mail server (and the Post Office) are to be considered as temporary storage, holding the data until the user downloads / brings his mail home.

Web-based e-mail is a relatively new thing and removes the user from full control over what happens to the data. IMO it's also a security risk. Leaving mail on the server makes it vulnerable to hackers. Anyone who hacks a server gets access to the data on it. GMail, Yahoo, HotMail, etc. servers are much more likely to get hacked than a user's personal computer.

Possible help here,

https://help.aol.com/articles/email-previously-listed-in-my-mailbox-is-missing

Of course, it's always possible to use a desktop client (e.g. Thunderbird) simply as a back-up tool, while still using the AOL web interface for day-to-day email work.

It's too bad AOL doesn't have auto-forwarding (as far as I know), or you could easily have all incoming mail automatically backed-up by sending to, say, a Gmail or Outlook account. Then again perhaps a Gmail or Outlook account could "POP" the AOL account (as long as you'd choose the "leave mail on server" setting, so it doesn't remove it from the AOL inbox). I myself have a FastMail account and it's set to auto-forward to three other free accounts I have, so I don't worry to much about losing emails. :-)

By any chance, did you use your aol mail account on an Apple phone? Asking because my email stays on "the cloud". If so, maybe you can check there.

No. Don't have such a device. Was on a PC laptop at the time of the loss.