The bushings on the rear end of the front control arms are in the general vicinity that you heard the squeak and they would see some motion when you are bouncing the vehicle. I'm guessing you already checked them as that would be pretty obvious.
One thought that just came to mind: It's always a good idea to loosen all of the control arm attachment bolts when you install your lift (if there are rubber bushings involved) and then retorque them when the vehicle is sitting at ride height. The reason is that after the lift the control arms will end up at a slightly different angle and, if you didn't loosen the attachement bolts and retorque them at ride height, the bushings will essentially end up with a slight twist (or a preload) at ride height. That could, perhaps, cause a squeak. The easy way to test this is to just loosen all of the control arm attachement bolts sufficiently that the bushings will "relax" if they have any twist, and then retorque the bolts. This must be done while the vehicle is sitting at ride height.
As a final thought, the front driveshaft attaches to the transfer case in the general area you heard the noise and it, too, will experience some motion when you bounce the vehicle. You might check to make sure the boot or shaft isn't hitting anything.