If you deleted a group or groups from itself from the audience page, the group itself is deleted but the contacts in it will remain in your audience. You can think of it like a container. The contents still exist even if you take away the container. This is what you will see if you are just deleting the group itself:
Not to worry! I jumped into your account and created a segment under the Audience tab called a Limbo segment. I creatively named the segment... Drumroll... "Limbo"! A limbo segment isolates any contact in your audience that does not belong to any group. Since these contacts do not have any group membership, we consider these contacts to be in limbo.
The process for deleting all of the contacts in a group or segment is essentially the same process. If you open the segment and click the "selected contacts" drop-down button, you can then switch your preference to "all contacts". One you have selected the "all contacts" button, click the button to the right that says "delete them". You will then be asked if you want to delete the contacts from all groups and your audience. Click the button to delete, and you're done! Those contacts will now be in your Deleted items folder. That process looks like this:
I hope this helps and please let me know if there is anything else I can help you with!