Sample apology letter for not attending function

Dear {Recipient},

I am so sorry that I was unable to attend {name of event}.

You might laugh when you hear the reason I was unable to go. {Story about not attending} Crazy, right? I know, I know. That could only happen to me.

I promise, at a future {name of event}, I will be there with bells on, ready to make up for all I missed this time around. So don't hold this against me, okay? I'll be expecting my invitation when you do this again.

Until next time,

{Sender}