Might have them take a close look at the "disc brake pads" and the rotor, if the rotor is out of spec a bit it can rub just enough to cause a squeak! One other odd item, have them check the "pedals", I had a damned squeak I couldn't locate, the main mech. and I figured it was comming from a "hairline crack" in the body of one of the pedals, repalced the pedal, NO SQUEAK! Also, put a tiny bit of grease on the seat rails or the seat post holder, that squeak drove me nut's, luckly a long time rider, told me to check that and it worked FYI.