Thanks for your comments. Finally got him home and after a blood test, x-rays, and other assorted things they determined he has an infection in his guts. I'm still in the "irked" section because it might've happened on a walk and I try very hard to watch every move they make so as not to nibble on something they shouldn't. I was told it could be anything out there that was licked or whatever. Our yard is free of any toxins and I'm always out with them when they go out.
I am pleased this is treatable with a couple of pills for the next week and I hope it will be fine. Just a tough thing to deal with.