I am heartbroken. My daughter moved out of State today with our granddaughter

Agree with BlueBelle & MayBeMaw be happy for your family and be glad they are moving on with their lives. You have helped them when they needed it so time now for you and your husband to enjoy your lives.

OP

Maybe your dd and sil told you they were moving out this way because they thought you would react less than favorably to the idea?

You also said sil left w/o a goodbye, what may have happened - any conflict, disagreements, etc?

HowToFindHope, as BlueBelle implied, your daughter well knew this would be shocking for you. This is quite a good sign as it shows that your daughter understands your feelings.
This is a big loss for you and we all hear your distress.

I don't think they could face telling you in the manner you'd have preferred as they knew how upset you would be. My daughter's boyfriend has just made a film called 'An Irish Goodbye' - it is a phrase used when someone leaves a party abruptly without saying goodbye.

It is fantastic you have helped them get onto the property ladder, I wish them luck and hope you can fill the space they've left in your life with good things.

I posted their age incorrectly they are both 26. I agree that is not young. I believe they were both immature the way it was handled. Of course their happiness is top priority no matter our feelings. But it doesn’t take away the sting. Our house feels so lonely and it’s quiet. I walk by the parks in the morning where we took our granddaughter a lot and the tears start and I feel like I can’t breathe. It feels like this heartache will never go away.

OP,

Let me ask you, how would you have preferred to be informed?

I disagree they are immature.
They must have put some thought in minimizing the impact it would have on you - that shows they care.

The result is still the same - they have decided to have a home of their own.

It was going to happen sooner rather than later.

It’s very early days but it’s up to you how you handle it, you can pull your big girls pants up, plaster a smile on your face, and get used to it or you can wallow and wallow and make everyone unhappy

The wise mother helps her chicks leave the nest safely not pull them back in

Howtofindhope try not to look for reasons to be angry with them, it won't help you at all.

I don't think it would matter how they told you, it would have hurt anyway.

I'm afraid they aren't responsible for your feelings, this is something you need to manage for yourself.

It is time for them to live their own life and for you to live yours.

Fill it with things you enjoy

Have they invited you to visit them OP? Have you made plans to go down and see them yet? How far away are they?
You can keep in touch with your beloved GD via Skype or FB. We do this with our GC in New Zealand every week. At least you won't be restricted from visiting and will be able to get there easily enough.
As others have said, plaster a smile on and start planning for the future

Bluebelle's responses always seem so well thought out.
I'm just shocked that after living with you for 4 years with the intention of saving to buy their own place that there has been no discussion over that time about how close they were to achieving that. Surely they must have been to view properties and yet they didn't mention it, is that right. Usually, well going by my kids they would have been full of it and discussed every step of the move. I do find it odd that they have just sprung it on you, why do you think they'd do that ?

This must have been a terrible shock for you. They should have prepared you more kindly. You must have formed such a strong bond with your GD , I can understand your distress.

I think it was unfair to drop this on you at a gathering of other people too. How far away are they? I hope you manage to come to terms with the separation soon.

This case reminds me of when a person breaks up with a partner in a restaurant.

I'd tell them gently that you were really hurt by the way they told you and the way your son in law left without a word of acknowledgement. You don't need to make a big deal of it but I think it is best not to pretend everything is okay when it isn't. You can still wish them well and tell them you hope for a great relationship going forward, but also make a space for your own feelings to be recognised.

I think they've been very immature in the way they let you know. And your son-in-law leaving without a thank you or a goodbye is just bad manners.
I hope your daughter and granddaughter said thank you for everything and see you soon when they left?

I think you and your husband have every right to feel annoyed and upset about how they've handled the whole situation.
What you do about it though is another matter.
I'm of the "least said soonest mended" school of thought, rightly or wrongly. It's happened. You can't change it. They'll never agree they did anything wrong and if you complain it'll make you sound needy.
Onwards and upwards Howtofindhope ?

I would think they were too scared to tell you - hence the note.