1955 Buick

[68z28kk]

If the car has been sitting for 10 months or more and the valve stuck on initial start up I would look for varnish in the fuel. Non leaded fuel turns yellow the longer it sits and will stick a valve very quickly. It takes carburetor cleaner or lacquer thinner to cut the varnish on the valve guides but with some time and technique it can be unstuck without pulling the head.
If this is the scenario that occurred I can explain how to unstick it if it wasn't bent from piston contact after it stuck. Clint