Radio knob no longer turning volume up or down, replacable?

[nelsonjmbf]

So i have a 2004 525i, the other day a friend of mine must have turned the knob really hard or something because when i came back to the car the knob was actually popped out of the panel to the point that as soon as i touched it it fell off and i had to pick it up and pop it back into the spot it goes but not it just spins and spins loosly. The screw behind the knob looks loose and flimsly sitting in the hole now but i dont know what it looked like before to compare, when you spin the button know it no longer makes the little clicking noise it did nor does the sound go up or down, i can still press the button to turn the radio on or off which is what makes me thing he may have somehow stripped it somehow or maybe i need to take it off again and tighten the screw that is behind it? i wanted to see what people thought before i commited to any way of fixing it, im thinking maybe i can replace button with a different one off one i find at a local pick n pull or part shop that is the same model, or is that too easy of a fix and im going to need to replace the whole panel?