Thats good news.
But do not be concerned about history repeating.
At the very end of the master cylinder is a port that goes to the fluid reservoir, when you push on the pedal the piston goes past the port covering it so it can pressurise the fluid in the cylinder and feed it to the brakes,
When you take your foot off the pedal the piston comes all the way back again and uncovers this port so that fluid can again flow into the cylinder to compensate for wearing brake shoes/pads or out of the cylinder due to heat expansion or runout at the drum/disc.
If you adjust the pedal so that there is no free play this port can be covered. it takes a while but eventually due to heat expansion of the fluid (it expands more if it contains water) , the whole system becomes pressurised and holds the brakes on. as you experienced.
I hope this information puts your mind at ease.
as a side note, brake fluid is hydroscopic, which means its keen to absorb moisture from anywhere. especially the humid auckland summer air.
this is why brake fluid needs regular changing.
The situation is made worse by old braking systems that don't seal the fluid from the outside air.
I assume that this is probably the case with your car.
A ridiculous situation really, why the auto industry continues to use this stuff is beyond logic.