It is not unusual for a subject teacher to invigilate a test or examination , held in a specialist room , say cookery , metal work or art.That teacher is familiar with the equipment in that room , and would be able to supply it to a candidate on their request , so that the candidate can continue to carry out the task set in their own way.
this is not unusual ,. Only when the exam forbids the use of extra items would the invigilator not provide them
The fact that people went into the room next door is not really that important in a practical subject.However there should be some supervision to keep noise to a minimum.It is unlikely that the examinees will have suffered in any way really by this intrusion upon their creativity.This would not be the case in say an oral or aural test , nor one where intense concentration was required, mathematics , sciences , languages spring to mind here just as an example.
I would try now to put this test /exam behind you , get some serious revision done for the next ones and the very best of luck.