I can honestly say in all the time I have worked at Sprint, never once cared about the external litmus paper on a device.
They go missing, turn red when they themselves are a poor indicator of much of anything. A sweaty palm taking out the battery can cause those to go red. Go find a Motorola Rzr phone, almost everyone I've ever seen has litmus papers are red irregardless of how nicely they have been treated.
Any good technician is not going to refuse you service based on that alone. If one does, simply ask them to open the device and show you liquid damage/corrision. But like I said, I have never, ever, ever, ever, ever seen any technician I have worked with make a big deal about an external litmus paper gone missing. It happens.
(I say external - devices have litmus papers on the INSIDE. I am pretty sure the last time I took apart an HTC Touch Pro, there was one right on the inside of the back housing piece. That one is infinitely more important than the one on the outside of the device. Then again, I can honestly tell you that a good technician is less concerned by that sticker and more concerned with the state of your circuit board and if there is any water marking, corrision, etc.)
Hope this helped clear some confusion and dispell some unneeded worry
