My Warlock just got a ring with the Artificer Infusion “Spell-Refueling Ring”, this infusion states:
While wearing this ring, the creature can recover one expended spell slot as an action. The recovered slot can be of 3rd level or lower. Once used, the ring can’t be used again until the next dawn.
However, I am a Warlock which means that at 7th level, I literally do not have any 3rd level or lower spell slots. Does the ring thus become useless at this point and I should just give it to another party member?