I have to call a lot of people in the course of setting up events, so...
if I feel I may have called at a bad time, I'll say something to the effect of
" Oh, I hear you're busy, give me a time when I can call you back"
Most of the times these folks wicked owe me calls &/or emails (geez, we are showcasing them so you'd think...

). I am always cheerful & upbeat--even if I could strangle someone--so tone of voice, don't dwell on apology~
Personally, I'm guessing call back in a couple of weeks--but I would field this one to the guys, PJ or hey..post a poll???