Actually some STDs can be spread even if you are wearing a condom. I don't think blood is a sign of an std anyway and if it was on the condom Im sure that wont be an issue. Herpes can be spread during the sheading period as someone with herpes can shead tiny bits of skin that can transmit. Warts also only requires skin-skin contact and warts are often on thighs/skin surrounding vagina rather than in. Probs nothing to worry about, but if I was you I would be going to see a doc for a check since it was a call girl....