Take the right wheel off the car, and look in between the disc and the caliper? try to slide something in that's really thin maybe a credit card? Have you tried pumping the brakes? Maybe tap the caliper with a hammer, to see if it un-seizes?
check to see if brake pads are worn evenly from left side to the right. a seized caliper will either not move and brake pad and it will still look new or it will worn much faster than the rest. also check for seized/sticking slide pins.