a case of what?? LoL

No you arent due any type of Compensation,no matter how much you paid for your tkt. You purchased a Coach tkt and thats what you got a coach seat.

As you said you had a free Upgarde but there are numerous legitimate reasons a carrier has for removing a person from there. 1- its Needed for cockpit crew, 2- FAM, 3- change of equipment and now less FC seats etc etc

Since you were the last person there You became the SOL person

Next time purchase a FC tkt