Hi bud,
It doesn't sound seized if it can be turned over at all.
Do you have a socket set? on the right hand side of the bike, near the rear footpeg, there's a cooling fan that pulls air into the shrouds. You can see it through the black mesh. If you have the right socket to hand, you can put it through the centre hole, grip the flywheel and carefully turn it (I can't remember which way, though...) to see if the engine is free. If you can turn it, it's not seized. It is supposed to turn one way, and not really the other. I can't remember which!
I would be suspicious of the bike's battery, to be honest. If your partner has a pair of jump leads, connect the bike battery to a car battery and see if it starts then. I have a sneaking suspicion it will, and the mechanic might have been fobbing you off.