I really see both sides of this. If I understand you right, you are saying that they could have chosen to promote you on your mon to fri shift, but didn't because you wouldn't work Sundays. If that's true, I can see your point. OTOH, if this is a situation where the company must be open on sundays, and they need that manager, or whatever position you would have been promoted in to, to work those sundays, that's kind of a hard call for me.
I get women asking me all the time on interviews if we're a "family friendly' company. After dealing with a lot of moms here, I know what this is code for. It's code for "can I come in and leave whenever the hell I want to because I have young kids and have to take them to practice and get them from school etc etc" and everyone else can pick up my slack because hey! I'm a mom!
And now I say, nope. We're not family friendly, nor family unfriendly. We're a business. It's a full time position. There are no flex hours. You get the same paid time off as the poor childless, no more, no less.
Is that hardass? I don't know. I do know what it's like to constantly have my schedule disrupted because an employee is not here, again. That said, I am talking about a small business. If we grew to over 100 employees, I might be more flexible. So it also depends on the size of the business and just how much your absence is going to effect others as well as effect the bottom line. IMO.