Apology Letter For Not Coming To Party

Dear {Recipient},

Please accept my apologies for not attending your party {last night/yesterday/etc.}. I wanted nothing more than to celebrate {occasion} with you; sadly, {reason} hence I couldn't make it.

I would have {called/texted}, but I knew you were busy with {host/hostess} duties and I didn't want to bother you. I'm sure all your guests had a wonderful time. I'm a little jealous, actually.

Anyway, {I wish you a happy birthday/congratulations on your well-deserved success/etc.}! Let's meet up soon, shall we?

{Your Name}