To my readers: please use this whenever/wherever necessary. Much appreciated.
Dear (say their name(s)),
I’m so sorry I couldn’t be at your (say event (e.g. ground-breaking, parole hearing, anniversary party)). I may be missed, but not as much as I’ll miss seeing you (add “both” if applicable). If there is one thing I know, it’s that only what I’m doing right now could keep me from being with you. Sometimes timing is everything, and if it weren’t for what I’m doing right now coinciding with your (say event, see above) you know I’d be there. I promise to make every effort to be there next time (NOTE: don’t read this sentence if it would be idiotic to do so (e.g. testifying as alibi in murder trial)). In the meantime please know that even though I’m doing something else, I’ll spend every (second/minute/hour; use best judgment) thinking about you. Perhaps, if I can get away early, I’ll be able to see you at the after party (NOTE: don’t read this sentence if it would be idiotic to do so (e.g. funeral))!!!
I’m sure we’ll talk soon. Please feel free to contact me through the reader of this note (give them your e-mail and phone number; NOTE: under NO circumstances should you give MY e-mail/phone/address or any promise of passing on any message to me). They are a good (friend/lover/relative (use best judgment)) and I’ll be sure to get your message (see above).
Best wishes and see you soon,
Your (friend/lover/relative (use best judgment)),