Do you have additional wire(s) from the switch to the junction box?.............Another connection? And since you don't KNOW.....maybe this never was hooked up correctly?
The switch always makes/breaks the BLACK wire........
Since you have continuous power there now......Let's see......Two cases........
#1.....Two sets of wires present......The POWER enters this box B/W(&grnd)......AND a switch leg B/W(&grnd).........
The Grounds are connected together and the POWER white is connected to the silver screw on the outlet......
The POWER Black is either connected to the brass screw.......OR.......The SWITCHED black is connected there and the switch is "bad"
#2.............The power enters the SWITCH box .........the POWER White wires continue on to the outlet.....With ground if present........
The POWER Black wires should be switched but since there is continuous power either the switch is bad or the wires bypass the switch?