This is by far the most likely explanation. This is especially problematic with older counter balanced swing arm halogens that may have dropped one or twice, when the pot metal gears mis-align and the light no longer stays reliably in place but swings down right on top of the keyboard.
The only other cause for that kind of localized warping might be a hair dryer in the hands of a doofus who kept it focused constantly one the one spot where the spill occurred vs swinging it across the keys.
If there’s no sign of dried liquid, put me down for a lamp or the sun. Some windows can focus sunlight - fires have been started this way. Not your fault, but probably not his either.
I suggest it isn’t worth worrying about. Just fix it. Make the customer happy. Move on.
Boy, that fits the look of those keys perfectly. I have a strong hair dryer that might almost do it, but a Wagner heat gun on low would do it every time. Someone might spill something, even water, and think that would be helpful. They could have just dumped the water out and used a simple fan and been fine. People sure have their brass to pretend they were not responsible for such obvious abuse.