So confused lol

I had my prenatal on last Wednesday, they did a urine test and a blood test and everything came back fine! The urine test came back with extra creatinine and protein, but the doctor said it's normal during pregnancy and not to be concerned.

The last couple of days my back has been hurting really bad, but I figured it was just pregnancy back pain. Monday I threw up a total of 9 times throughout the day. Tuesday morning comes and I throw up right away, I go to the hospital for an IV since no where else is open and I'm feeling really bad.

Hospital Dr orders urine test, comes back and tells me I have a kidney infection

Wouldn't they of caught the uti at my last appointment with the urine samples?? I'm so confused lol