Two lines are enough to hold a whole friendship, or a romance, falling apart. The speaker looks back a year to a night when talking came so easily that neither person wanted to hang up or go to sleep. Three in the morning suggests the kind of conversation where time disappears and you say things you wouldn't say in daylight. Then the poem jumps to today, and the same person has become someone the speaker can't even greet.
What stands out is how small the problem looks and how heavy it feels. "Hey" is about the simplest word there is, yet the speaker is stuck on it. The repeated "even" makes the sentence sound a little tangled, as if the speaker is frustrated with themselves and almost embarrassed. The poem doesn't say what caused the distance, and that gap is part of its ache.
The mood is quiet, wistful, and awkward. It captures the strange sadness of losing closeness without any big fight, just a slow drift into silence.