Is there a way to see what I wrote on the chat?

I'm not sure if this will work since the person that posted this posted it 4 years ago. But you need to go to

-/Library/Application Support/minecraft (Your Minecraft folder)

Then in that folder go to Logs. Most of the files should be zipped so you'll have to unzip them. But in those files should be all of your chat history.

In your Minecraft data folder (by default %appdata%/.minecraft on Windows and ~/.minecraft on Linux) there is a folder called logs. It contains the file latest.log for your most recent launch of Minecraft and a lot of .gz archives containing log files of previous launches. In one of those should be the chat log that you want.

If you want to search through all of them, you can copy the archives into a different folder, unpack them all there and use for example Notepad++ to search through all files in that folder.