I’ve seen this happen usually when the paperwork has been returned by those who have assumed that those details will do & don’t have access to case law. No offence intended to anyone involved to date in your case but the tribunal paperwork I’ve seen submitted on my behalf was incredibly involved & complex. The more ammo you can put in the panels hands the more likely they are to find in your favour.
I would strongly recommend getting in touch with fightback before doing anything else
They have a priority subscription service for a monthly fee where you get priority contact etc you can join that & get responses or use their Facebook page & talk to them for free advice.
My MR & Appeal ultimately cost me £300 for all their paperwork & submissions & I only paid that after I got my back pay. They submitted hundreds of pages of stuff too it was amazing.
I wonder if the telephone tribunal is a grounds for appeal in itself, definitely talk to either fightback or a welfare rights person they’ll get you straight. I’m sure given the right advice you can make moves to get this mistake corrected.