Was this a marking compound on anodised ally? There is no ways that laser engraved anodised ally (leaches the dyes) can have the lettering "rub off"
Most anodising has a sealant applied - the anodising is merely a porous layer that absorbs a dye (to colour it) and then is sealed after colouring. If you used a marking compound on natural (which is still sealed by not dyed) then you might have had issues with the sealant not allowing the mark to be truly permanent.
Rodney Gold, Toker Bros trophies, Cape Town , South Africa :
Roland 2300 rotary . 3 x ISEL's ..1m x 500mm CnC .
Tekcel 1200x2400 router , 900 x 600 60w Shenui laser , 1200 x 800 80w Reci tube Shenhui Laser
6 x longtai lasers 400x600 60w , 1 x longtai 20w fiber
2x Gravo manual engravers , Roland 540 large format printer/cutter. CLTT setup
1600mm hot and cold laminator , 3x Dopag resin dispensers , sandblasting setup, acid etcher