I just wanted to post this so that others don't nearly have a heart attack as I almost did. When deleting a Power BI Group, after clicking the "Delete Group" the Service shows you in your own workspace, and all datasets, reports and dashboards are gone... So it looks like you just deleted everything from your personal workspace, Keep calm, and refresh. Things pop back to normal with a little love from F5.
I think my blood pressure has stabilized from 2 hours ago thinking I had some how mistakenly nuked my entire workspace.