You are entitled to your opinion. However, "being on disability" is not a protected characteristic under the law and therefore does not offer any special protections.
When and if you suffer some actual health issues that you and your doctor are able to tie expressly to the fact that you had to attend this meeting, and can provide clear and convincing evidence that you would not have suffered these health issues if you had not had to attend the meeting, come back and see us then. Until such time as your health is drastically damaged by your attendance at this meeting and you have medical confirmation of that fact, it's no harm, no foul.
Two things I am tired of typing: 1.) A wrongful termination does not mean that you were fired for something you didn't do; it means that you were fired for a reason prohibited by law. 2.) The above answer, whatever it is, assumes that no legally binding contract or CBA expressly says otherwise. If it does, the terms of the contract apply.