Anxiety is such a horrible thing...makes so many physical symptoms come out and generally make one's life miserable. I've been dealing with it longer than I care to!
Anyway, I think blood can be in your urine for a countless number of reasons, many temporary and benign. Actually it's pretty amazing our kidneys filter our blood and don't hardly let any blood pass through to begin with.
Hang in there...sounds like you've made it through the surgery great and on your way to recovery.
Post often as we all have been where you are anxiety-wise and can offer advice as well as support!