i can't find my chats

I just came back. Last time I was here was 1 or 2 years ago.

I still remember so clear everyone I was talking with.

But I can't see my chats anymore. Not even their names.

When I logged, I saw some text from just 1 person. I clicked, but the messages very empty.

After I typed, it appeared another icon of old friend, clicked, but chats were empty as well.

Why chats are being deleted, even that I wasn't able to read them?

And my other question is, is there a way to browse my chat history?
I want to meet my old friends, this is so sad