I think the relevant question you didn't ask is "what should I do to minimize the damage to the company and my career?"
Everybody makes mistakes, it's a basic fact of life and happens all the time. What's important is how you deal with it. There are actually many formal failure analysis methods that are employed in corporate life (8D, FEMA, Ishikawa charts, etc) but most boil down to
- Fess up: communicate open, honestly, and accurately
- Damage control: salvage what you still can, ask for help if needed.
- Analyze: what went wrong? How could this have been prevented?
- Corrective action: What will you be doing differently in the future so that does not happen again either for you or for anyone else in the organization
The last step is the most important one. In this case it could be something easy: have a pre-vacation check list in place, implement an automatic notification system for "last day to cancel" events, have a shared calendar for bookings that other people can see, etc.
Dealing with mistakes is one of the more important ways how an organization learns and gets better. Most mistakes are easily forgiven. Making the same mistake twice is typically not: Because that means you have failed to learn from the experience.