Reoccurring appointment dropped off calendars

[Melody4572]

I sent an appointment to several people both in house and in the "world" We
have Outlook 2007, and use an exchange server. My appointment is still on my
calendar, but seems to have "dropped off" the people in house. When I resent
the reoccurring appointment I received Status: 4.4.7 error messages for the
people outside of the office. My questions are:

How could it have dropped off everyone's calendar in house. And why did it
fail to reach the outside recipients?  

Thank you for any assistance in these questions.

 

[Melody4572]

I wanted to add more information

The original appointment went out in November of 08, so it isn't over a year
old. It was set as reoccurring. Other reoccurring appointments have been
sent to these same people, and they are still there and have not dropped off
anyone's calendars. It was not sent from anyone else's as the original is
still on my calendar and the original email message is in my sent mail
folder.

As for the error message, my fault for forwarding the original appointment,
not resending or sending a new one. So I just need to know about why it
would have dropped off people's calendars.