i have had to relieve myself in another manner before and had a young buck sniff it... like nose to the ground gettin a goooood whiff, stepped back a lil confused looking, and continue on the way he was going...
I rele dont think that human urine will spook a deer to terribly bad. like you said though, i still carry a water bottle (and tp) with me, just in case.
Also, that tp can be useful for marking blood while blood trailing