Possibly the form got lost in the post. If you have a mental health problem then an unreturned form would not result in the claim being ended. I would ask for an ESA50 to be sent out, it is to your advantage to fill this out as it gives you a chance to explain your situation in your own words.
Hi Carolyn I have a friend who had the same happen just recently, he attended, and was informed last week that he is still in the support group, 2 other people I know, had the same result, so who knows Rapheal