Reaching for your phone is an example of what psychologists refer to as avoidance behaviours. We look at screens so that we don't have to deal with difficult thoughts and emotions.
Sure, without a phone that person had no other choice but to face whatever they've been avoiding. But more often than not leaving someone to their own devices when they clearly can't cope with the situation by themselves makes them look for a different source of distraction that in turn will make you wish they were "just" addicted to social media.
A person doing well mentally has no need to avoid anything. The right thing to do is help them get there, not play whack-a-mole with their coping mechanisms.