TBH if you saw white discharge, it could be mucus. Gross as it is, a vagina pushes some out at certain times of the month (ovulation).
Obviously, it could also be spunk, without being there, with a gyno kit. We will never know. Also slightly gross, most women will discharge the offending spunk pretty quickly, regardless how far up you get it. The vagina is self cleaning, it pushes most stuff out. So there wouldnt be much left up there from a previous client, if she was up and about prior to your meet.