I can certainly understand why a person in that situation might not call back to chat.
But if I were the one in your shoes, I would consider my not listening to the message to be a mistake. (I make mistakes all the time--I can live with that.) Because my reasoning *for myself* would be that listening to the message really doesn't take that long.
I think the key here is that you decided there would not be anything of any substance in the voicemail. And this time you were wrong.
That set off the entire chain of events. Only you know how risky that decision was. In this instance, you "lost" the gamble.
(Also, I don't think there's a real need to apologize for missing the party; to me the "offense," if it can be termed that, is the "not listening to the substance of the email." Not that I'd want to say to my mom, "I'm sorry I didn't play your message." That would probably tick my own easy-going mom off, if I said that to her. So were I in your shoes now, I'd leave well-enough alone, and try to remember to actually listen to the voicemail next time--and THEN wait several days to return the call.)
(As I said, my own reaction is probably greatly colored by the fact that my mother never, ever called me just to chat. There was always some sort of "business" that prompted the phone call. And that is true of me as a mom as well, and of my DD. We don't make contact unless there's actually info to flow one direction or the other.)
(edited because the tone of my original was WAY too harsh!! Sorry)