Unfortunately, there is no easy way to identify that. MeetingPlace doesn't have that kind of audit mechanism.
You would need to know an approximate time when the user was created, collect the System Information Capture logs and then review the logs for any activity (you need to review multiple log files, trace actions, etc.). It is a rather complicated process to identify this kind of an activity. If you at least have the approximate time when this took place, and it is not too far in the past, there still might be logs available on the system for review, so opening a TAC ticket would be a good step.
Sorry I can't help you more with this.
-Dejan
