Log in to QQ on your computer and open a chat window for your friends.
Then we click the inverted triangle icon in the upper right corner of the friend chat window. Then we click more settings in the pop-up options.
After clicking, we click permission setting at the upper end of the window. Then click temporary session.
Finally, click the screen contact management on the window to retrieve the QQ friends we deleted a few years ago or even a long time ago, because when we delete each other, we will also screen each other's temporary sessions. （ShouJiQQNengZhaoHuiQiBaNianDeHaoYouMa）