Hey Rob,
I hope all has been well 🙂
If you’re using a custom template override as explained in our Themer’s Guide, you should be able to move the code calling in the attendee list back into your sidebar.
As far back as I remember, the list of attendees has always been beneath the event details, so I imagine you’ve got a file named single-events.php with the following structure: [your-theme]/tribe-events/single-event.php.
I’m pretty limited on these types of requests (see What support is provided for license holders?), but if you get hung up, feel free to reply back and I’ll do my best to help.
Thanks and have a good evening. Cheers!