The group chat remains open, even after the meeting. This way you can arrange the next meeting directly.

If you want to find a certain user with whom you have been to a meeting, you can proceed as follows:
Either you look under the tab "Chats" under "Acquaintances" - there you will find all users with whom you have been on a meeting together or you go under the tab "For Me" to "Completed" - there you will find all completed meetings in which you have participated. Now search for the meeting that you and the other user attended together - you should be able to find the user again :)