No way to hide it
I've been having sex with a guy for a few years now. Most times it's at his house pretty late. He doesn't live to far from me. I happened to be just off work when he texted me. He asked what I was up to. Told him just got off work. He asked if I was still in that area and I told him I was. He asked if I wanted a blowjob. I'm always up for that seeing as my wife hasn't done it in 3 years.
I pull into a parking lot and to a spot that had no cars near it and not a lot of traffic. He gets out of his car and into mine. I drop my pants and he starts sucking. About 5 minutes into it a girl I work with (flirts with me often and is incredibly hot) walks up. I must have not paid any attention to her. My window is rolled down. I'm slightly layed back on my seat. She walks up and says, "Hey Jason, what are you doing over here? Oh wow..."
I couldn't hide it. I had my boyfriend's mouth on my cock and he was going for it. She said, "Well, I can see you are busy. I'll catch you later."