@Scott Christian
In the spell description, there is no "may". The Charmed condition happens on a failed save. What remains unclear is if the target knows they are − or were − under this condition. The game rules must make this clear.
FRIENDS
Enchantment Cantrip
Casting Time: Action
Range: 10 feet
Duration: Concentration, up to 1 minute
You magically emanate a sense of friendship toward one visible creature within range.
The target must succeed on a Wisdom saving throw or have the Charmed condition for the duration. The target succeeds automatically if it isn’t a Humanoid, if you’re fighting it, or if you have cast this spell on it within the past 24 hours. The spell ends early if the target takes damage or if you make an attack roll, deal damage, or force anyone to make a saving throw.