Yeah, my rear brakes did that a few times. The last time I was not able
to brake it loose by using granny gear and reverse so I took off the
wheel to smack the drum with a big mallet. After a few good whacks it
popped loose. From then on if I know my brakes are cold and wet I will
not use the parking brake. Likewise, if the temps go below freezing and
the brakes are wet and cold they will freeze to the drums. Then it's
time to get the torch out to heat 'em up. My dad used to build a small
fire under there! Bad idea!