Sometimes we find that even though a strata manager may appear not to care, the strata manager's manager does. You could try escalating to the next level up within the strata company?
If that leak was incident-related (i.e started then stopped with the tap replacement or defrosting of the fridge) maybe both the plumber and the resident flooded the floor both times and then it soaked through? If that's the case, the leak is over and the building should be OK.
If the leak occurs periodically or is now continuous, it could be a slow leak that drips through onto the plaster, takes time to build then pours through the ceiling when the volume of water overwhelms the soaking ability of the plaster (!) An undesirable situation for you, the owners and the building.
Either way, the cause must be determined asap so the owners know if the buildings structural integrity is at risk.