I have a user that created an appointment/schedule on a shared calendar. Problem is that he can't see what he created on the calendar on his computer. Everyone else that can view the same shared calendar can see what he created. What setting is he missing that he can view what he created?

How are you sharing the Calendar? Are you using an Exchange Server? Does it reside in Public Folders or in another Mailbox?

Check your permissions on the Calendar.
Reviewers can view items only.
Authors can edit items that they own.
Editors can edit all items.
Owners are allowed to edit all and set permissions.

Note: Sharing works only on server based mailboxes and Public Folders. Personal Folders (PST files) are single user files and can not be shared or opened by more than one person at a time.