Ah, yes, that chime you get when a loved one messages you. It's addicting, and the silence when it is gone heartbreaking.

The phone's stayed on.. yet silent,

I like how you work with the traditional 'stuff' of a love poem ("epistles to me", which suggests an actual love letter, on paper), but rework the form to fit our modern era with the phone, which can also now contain epistles. And I also like the double meaning in the last line, which could refer to both the speaker and the phone itself (I imagine the speaker scrolling through the old messages on FB, memories held by the phone.). Nice poem!