In bash, is there a way to echo/print the last stdout? Is there a variable that stdout is assigned to?

Nope, there's no way to see a line sent to stdout unless stdout's already been sent somewhere. If it was sent to a console, copy the text from that console. If you sent it to a file, tail -n 1 that file. If you can re-run the command which generates the line you want to see, I would suggest piping it to tail -n 1 to see just the last line of output.

Bash keeps a history of executed commands (~/.bash_history by default in GNU Bash 4.2), but not of output.

Try adding |tee output to the end of your command.

If you want to capture the terminal output of your entire session, try script(1).

Also, this questioner is looking for the ability to search command output, so check answers there too.