Hello, the ad-hoc meetings (Meet now) are not scheduled meetings but do generate the attendance report, and will show the chat etc. if that's been used.
So you should look in the Chat to the left in the navigation bar if it was started in your own Teams calendar. If it was started in a channel you'll find it in the channel under Posts.
If you can't see the attendance report that setting is probably not enabled in your Teams meeting policy. Reach out to your IT admin for that.
-AllowEngagementReport
Determines whether meeting organizers are allowed to download the attendee engagement report. Possible values are:
Enabled: allow the meeting organizer to download the report.
Disabled: disable attendee report generation and prohibit meeting organizer from downloading it.
https://docs.microsoft.com/en-us/powershell/module/skype/set-csteamsmeetingpolicy?view=skype-ps