Separation anxiety?

In an earlier post, I mentioned that Mochi stayed at Jenny and Joey's house while we went to Vegas. We later found out that soon after we left, Mochi threw up a few times, and he proceeded to throw up a few more times the next couple of days. It could have been related to the rawhides Jenny gave him each day, but Joey had been eating those before he arrived and didn't have any problems. We suspect his unease was due to some separation anxiety. He got better as our trip ended, and he had no problems when we brought him back home. Our sensitive little guy...