There is no reason for you to worry at all about STD or any sort. Penetration is needed for transmission to occur. As for your possible discharge, I am confident it was not an indication of infection. Sometimes after an exposure that, in retrospect, one wishes they had not had, persons tend to examine themselves and be far more attuned to genital sensations than in periods when they are not concerned. This in turns leads to noticing what turn out to be normal secretions or sensations that might have been not noticed or ignored at other times. Perhaps this was a contributor to your situation.
Take care. EWH