If a male friend calls his friend sweetheart should alarm bells start ringing?

First time my friend called me that last week. He's not effeminate of anything, and no gay things have happened. Well I never said anything at the time, apart from nearly choke on my coffee. I thought maybe a slip of the tongue. He is a good friend, and I know hes fond of me so didn't like to say anything. He usually just calls me my name or mate though.
You don't know how to feel really do you in that situation. I mean I was shocked but I suppose I should take it as a complement, as long as he dosen't get in a regular habit of calling me pet names.