My boyfriend sent a suspicious text to a girl.... what do I do?

My boyfriends has a pword on his phone, so this has always made me a little bit weary of what he could be hiding on his phone if anything. He was using his phone then left it open whiles he took a shower, so I used this opportunity to look at his messages and found he had sent a message to a girl saying ' I thought you wanted to spend sometime with me..' with her replying ' I do want to spend sometime with you'. I asked him about the message and he explained that this girl had invited him to an event and he didn't want to pay so he said that to her so she would put him on a guest list for free. I'm not sure if he's answer makes much sense....what should I do?