I prolly already know the answer but I'll ask anyways. I had about 300 read messages in my inbox and they simply vanished. I have several other folders inside my account and all of them are intact. These were not super important but there were some that I would like to have back. Am I screwed or what? I have changed my password just in case someone got into my account.

It might be possible? Check in spam folder, deleted items and others...

I might contact Yahoo for support also.