When you say "they took the ground out", did they disconnect your hacked grounding when they pulled the audio unit out while fixing rattles? Don't panic yet. I would just go through every step of the hack and verify that all the connections are still there, and if anything disconnected - reapply it again. If that not going to work, try to reverse the hack and connected it the way how it was originally to see if it gets back to original setup and operation before the hack. Now, if that's going to fail, bring the car in to your dealership with original connection setup. Based on Lexus warranty, any hacks you do to your car voids that specific part of it. Also, I wouldn't discount if they decided to teach your a lesson since you hacked the system and *fixed* it themselves? Either way, just go with steps of the hack to verify everything, and if it doesn't work, re-connect it back to original, and if that fails - take it to dealership back. Make sure to be extra nice to them. Going back and blaming them with attitude not gotta help you