It's sad to be so far away, but I'd be prepared to give them the benefit of the doubt. It is stressful moving, especially with a family, and they must still be sorting out and settling in if it was last month. Also, they have tried to contact you but you missed the calls. It might be better to show willing and keep your sound turned up so you can reach each other any time on messenger. As other posters pointed out, communication has changed. They probably feel facebook and messenger are the best/most immediate ways of keeping in touch as they are so far away. Do they use FaceTime or Skype - have you asked for a virtual tour round their new house? I'd send an e-card to your SIL, and e-gift if you want (much easier anyway), and remind them about a contact number in case of emergency. People rarely change their mobile numbers these days so do you know that? I remember being a busy parent and feeling so guilty because one older relative always said 'I never hear from you/I thought you'd died' that I stopped phoning altogether. I can't take it back now and years later it still bothers me. It's really hard when you miss your DD so much and seem to be just one part of their lives, but you're right in being happy that they are happy.
Trigeminal neuralgia and medication