Air Leak at or near park brake switch

The "switch" is actually a push pull "valve" with airlines and valving in and out behind the yellow knob. Its Not unusual to go bad and need repair or replacement. any truck shop can repair quickly as its a std part. Or you can get behind it yourself and see if a line going in or out is leaking or its the valve itself (replace) This is a Fix it before driving much part , it can leave you stranded on the road.

Shouldn't you expect to find a split air hose?

Likely that the valve has gone bad. Open the dash and confirm that it is leaking then pull it out and take it to truck dealer or someplace that deals in air brakes. It isn't an uncommon failure.

You will prodadiy have to remove the switch to investigate.