This also applies, on a larger scale, when one adds data to a medium like a sheet of paper, the graphite or ink adds to the mass of the storage medium. But does this constitute data? The maximum mass would be achieved by covering the entire sheet with graphite/ink which, it could be argued is not data (unless you consider it to be a binary cell in a larger byte of data). I don't know the physics of thermal paper, but I suspect that it might be the opposite. My point? This is not evidence that data has mass, it is evidence that transcribing data onto a storage medium may change the mass of the storage medium, and that change maybe positive or negative.

Perhaps I should have this carved on my tomb stone...