What should I do if I find an incriminating text on my boyfriend's phone?

So, he tells me to look at his cell whenever I want because he has nothing to hide. I browsed his texts when he was in the shower and I saw he sent a message to his buddy saying "Ughhhhh I really want to be single again". What does this mean? Is this just guy talk? His buddy never replied so there was no more of that conversation. Or it was deleted. Should I be concerned? We've been serious for a while...