Has anyone ever had a dog dropped off with a urinary tract infection?

Friday (yesterday), a client dropped a dog off at my house for three nights of dog boarding. Within 2 hours, I took the dog for a walk and noticed there was blood in his urine. I called the owner; I contacted http://Rover.com and took photos of the very red urine. It was especially noticeable when he peed on a white fence. The owner made a veterinarian appointment for this morning at 8:30 AM. I took him in at 8:30 AM, and after waiting until 1:30 the vet said the x-rays came back negative for bladder stones, but the test results for the Urinary Tract Infection wouldn't be back until Tuesday! So they didn't send me home with any medication. I'm worried the dog is in pain, although he is acting normal, I know UTIs can be painful. And I'm surprised the lab is taking that long to process the results.

Has anyone ever cared for a dog in this sort of situation before?