That was theft, absolutely. I've traveled through PHX numerous times with empty Lexan or stainless steel water bottles, only once being asked(!) if the stainless 14oz bottle was empty.

Too late for your partner unfortunately, but you could have escalated to a supervisor, claimed availability of water to be a medical necessity for the bottle owner (as it is for all humans, broadly), or asked to "take it back to the car" and tried another checkpoint, if you had time.

PHX has always had its share of bad screeners, but the occasional decent supervisors I've dealt with in the past all seem to be gone. If they try to confiscate my unique, name-engraved "volunteer recognition" stainless bottle I might consider escalating the matter to the PPD, but given the subornation of perjury a PPD officer apparently committed to get PC for Yukari Mitamae's arrest, that might do more harm than good.

Very sorry to hear about your other half's experience. The item may be of low monetary value, but the implications are serious and horrifying.