Bo's scare

We have a pupper that is under the weather. :( Yesterday I took the dogs to their favorite doggy day care, I do this once every 2 weeks for their socialisation with other dogs and just to break up the routine sometimes. I talked with the ladies there and Bo and Bella were fine all day. The drive home was uneventful, and I was looking forward to go out on a date with my husband that we had planned. When I got home, Bo started coughing. And not a normal, I accidentally swallowed something I shouldn't have, cough but a weird snort/cough/retch. It was scary to see because he was hurting, and Jon and I were clueless. We decided to watch him to see if it was something that passed... but after an hour he was still feeling bad. We loaded the crew up and went to the e-vet. They did an exam, the did x-rays (multiple) and after all the time and $$$$ they came up empty. Nothing wrong could be seen or heard, and the whole while, not a single cough. As soon as we got home he was huffing again, so I'm still a nervous wreck. This morning he seems a little better, but we are keeping a close eye on him. Poor Bo. :(