I'm not quite sure that I fully understand what's occurred. But it seems that you are claiming that you were removed from your position to allow the assignment of a disabled employee who could no longer perform the duties of his position. You were assigned to another position without loss of pay.
There is nothing in the ADA that requires an employer to displace another employee to accommodate a disabled employee; however, I suspect that nothing in the ADA prohibits it either. Since this seems to be a rather novel, I suggest that you discuss your situation with EEOC or the state equivalent.

