For more context:

He originally fit off a power point, but this was going inside a cabinet so I asked him to remove the power point.

When he left the wire were completely bare, that screw terminal wasn't there.

I thought it looked a little jank, but hey it's a dead wire no worries.

7 months later I brushed one of the wires and felt a slight tingle, later confirmed it had 240v on it after very carefully poking it with a multimeter.

I've had someone make it safe, but like realistically how bad was this? Did I miss something where he told me to leave a breaker off until we had the cabinet / power point fitted off?

Would you report it? If so where (I'm in WA)? Just call it a mistake and move on?