Hi Michelle,
I have to say that I'm not certain about this, but I would agree with you that you remain entitled to IS rather than ESA.
Unfortunately, the only way of being certain sounds like another visit to the CAB. As they should have all the case notes from your last visit they should be able to answer your question reasonably quickly.
Good luck,
Steve
Nothing on this board constitutes legal advice - always consult a professional about specific problems