Having a lock on a door is not obstruction or hindrance, it’s just normal. Cosmo is right. Re having a non-approved lock – that would be relevant if there were a fire.
My other half left the bath running which resulted in a flood, and water pouring through the downstairs ceiling. The neighbour called the fire brigade who broke the door down, we thought that was fair enough in the circumstances.
The answer to the question lies with the cause of the flood. So what caused the flood? However, the neighbour doesn’t owe you any duty of care.