vina, you don't say where you live, but some places have grandparent rights. You need to call a family law center or lawyer and find out in your state, what rights you have.
I think your granddaughter is really at great risk for abuse (or at least neglect) in this situation.
I do agree with Margy, that the first step might be to just apologize (although you have nothing at all to apologize for) and express to your daughter that she might want date nights once a week or so, and you'd be thrilled to take care of the little girl if she wants to go out.
If that doesn't work I really think you need to seek mediation. This is the EXACT situation where children are at real risk for harm.
Best wishes. You sound like a wonderful grandma, and I hope and pray your grandbaby can come back to be with you.
I am sorry it hurts doesn't it, all I can suggest is that you try to befriend them ,maybe take a gift for the child around to their house , speak to your daughter first and tell her how you feel, may have to eat some humble pie,but that may be worth it to get back on a good footing .. then do what many have to do , keep it zipped with the man in her life ,when it comes to confrontation. Good luck many go through similar ..