You think he told the truth

My bf is at the beach & he told me he was staring into space like into the water. & he said he was zoned out & realized this girl was staring at him. He told me the girls bf noticed her staring & flipped him off because he thought my bf was checking his girl out. I'm not sure if he told me this cause he actually was & wanted to make me jealous? Cause why would they guy flip him off unless it wasn't direct.. just curious. Lol i get jealous don't judge please.