Did they watch him at their house or yours? If theirs, is your baby used to your daughter's home and to your daughter?
Both my boys had terrible separation anxiety. The problem I had was that when I would go to work, Jake would get really sad and mope around all eve while I was at work, even though my hubby was here with him, and he plays with him and spends a lot of time with him. But, he's a mama's boy. He got used to it and was doing good. Then, I got sick and had to be off work for awhile, so I was always home with him. When I had to go into the hospital, he had a hard time. After I went back to work, I had to start over with his separation anxiety. Now I'm off work again, and I have two that are mama's boys.
Here's what I do: Everyday, even if I'm not going anywhere, I take my keys and purse (they associate that with me leaving), and I go outside for a little bit. I started out just going for a couple minutes at a time, and gradually increased the time. This helps a lot because it makes them realize I'm always going to come back. If I have to leave for an extended period (like if I'm in the hospital), I leave them each a shirt with my scent on it. My daughter stays at our house with them. They are very used to her because she is here a lot, although she has her own apt. She said they do sleep with my shirts, so I think it does help. She also sometimes takes them to her apt. for a few hours to play with them and so that they are familiar with it in case she couldn't come to our house to watch them in an emergency.
Maybe you could leave him with your daughter a couple times a week, just for short periods of time while you run an errand or something. Get him used to being left with her, and he will see that you are coming back to get him. I think correcting the problem to set his mind at ease would be much better than medicating him. Good luck to you!
