There is one more aspect that you might have to look into. It could be that friend messed up the throw of your pedal. Let me explain a little further.
The pulley in the pedal does not cover the whole rotation of the pot therefore you need to set up the endpoints of the effect.
In order to do this, unscrew the bottom plate, and take the white retainer out so that you can release the pulley from the fixed position. Turn your Q full on, and experiment with pot. Once you find a part of the range that you are happy with bring the pulley back in and screw back the retainer.
I messed this up as well once, after cleaning up my pedal once. The cool thing about it is that I found out about this and I actually changed the range of the pedal allowing to start sweeping from a lower frequency.
If this wasn't clear I can make some pictures for you.
I used to be d*ck but now I am trying to be a dude. Some people don't get the difference...