When it locked up the clutch would not disengage the transmission. Did it do damage there also? What about the engine going from running at highway RPM to immediate stop? Did that do damage?
In these circumstances, the clutch would not disengage the transmission, because the problem is downstream. If the clutch pedal was kept fully depressed during this manoeuvre, from the instant that the bevel box seized, there is a reasonable chance that the engine is unharmed. Could the engine still be fired up afterwards? There may be some gearbox damage.
Anyway, you are lucky that it did not end up worse.
