Silver level detective
For the next two days, Max used a lot of methods to look for this Matrix guy. But to his utter surprise, he didn't even find his shadow, no clue at all. This man left no traces at all. Thus, this case was closed just like this.
Since half of the gold was still retrieved nonetheless and Robin also acknowledged to being the mastermind, he was considered as the culprit. And without any trace of his existence and previous criminal record of Matrix, the authorities think that there is no such guy at all.
According to them, Matrix was just an imaginary person created by Robin to shift the blame and keep the other half of the gold hidden. This way, it is no longer Max's responsibility to find out the gold's location from his mouth. This interrogation came under police's jurisdiction. Although Max felt that Robin really wasn't lying about Matrix, but after not finding anything to prove his existence even after a few days, Max was forced to let it go.