Participant/attendee able to speak to panelists during practice session?

[megant1]

We had a webinar today.  The panelist was running late so I emailed the participants to let them know.  When the panelist got into the practice session and we starting getting ready (I had not started the webinar yet) we heard a voice say "Is the webinar starting at 12:30?" I let them know if was supposed to start at 12:00.  Was this a participant who was somehow able to speak to us in the practice session?  Or someone with Zoom?  It was so strange.  I didn't think there was a way to communicate with participants before you officially start the webinar or vice versa.

[AnnikaZoom]

Hi @megant1  - if the host hasn't started the webinar, the attendees will be in the waiting room - and not seeing anyone in the webinar. 

And once the webinar is started, attendees is not able to speak unless the host specifically allowed them to do so. 

So it does sound like a very weird experience! 
I would recommend that you check that you haven't shared a panelist link with the attendees. If authentication is not required for panelists, anyone who clicks the link can join. 

If you want to follow up and understand what happened on this particular webinar, please contact support and provide the webinar ID and time and date.