Me: you find a ring that glows with magical energy

Sorcerer: I use Knowledge Arcana to identify *rolls a nat 20*

Me: You see that its a ring that has been enchanted with the spell Invisibility

Several Minutes Later in Battle

Sorcerer: I put on the ring of invisibility

Me: You put on the ring it shimmers with magical energy for a brief moment before turning invisible on your finger as if you were not wearing a ring.

Sorcerer: GODS DAMNIT!