Based on the wording of absorption (for the rod and ioun stones), I'm not sure if you can cancel spells that you can't perceive or not (spells requiring no components):
While this pale lavender ellipsoid orbits your head, you can use your reaction to cancel a spell of 4th level or lower cast by a creature you can see and targeting only you.
Counterspell requires that you be able to perceive a spell being cast, to react to it being cast, granted the wording of how counterspell works is slightly different:
You attempt to interrupt a creature in the process of casting a spell. If the creature is casting a spell of 3rd level or lower, its spell fails and has no effect. If it is casting a spell of 4th level or higher, make an ability check using your spellcasting ability. The DC equals 10 + the spell's level. On a success, the creature's spell fails and has no effect.
- With counterspell, you interrupt a spell during casting, but with absorption, you react to a spell once it has been cast, if it targets only you; at least that is my interpretation of the wording.
- The wording of absorption does require that you see the caster, which implies that you can't simply react to the spell targeting you alone without some kind of prompt (if you couldn't see the caster).
I'm completely split on whether you should be able to use the ioun stone of absorption to cancel spells that don't use components, but I can't find any rulings on it.