I have had sucess on another matter using the email comment form. Just fill in whatever additional junk information needed to get it to work. Took them two weeks to reply, about a month ago. You might also try to call, but that didn't work for me, the people I got had no idea what I was talking about. You could also try @FrontierCare on twitter.

That said did your account expire? They recently changed the expiration time to 6 months. Others have also reported miles going missing.