Upon rereading this, it actually might have happened if the thing that was unplugged was your phone extension. If so, then the landline in the other room might have rung. R. has a landline which he never answers, and he tells me it rings all the time.
But if it was all a dream, then it's interesting that the phone had an old-fashioned ring and sounded like the call was from a distance. I wonder who would have been on the line if you had picked it up? Your mother or your late partner? You, from the past? Ennis, although he didn't have a phone?