Hi,
You can try the Advance Search option in the shared calendar folder.
And I would suggest to switch the shared folder to Online mode to see if it can help:
Did you every make any progress with this? I currently have a ticket open with MS about this... I have a lot of unhappy users who want to be able to search like they used to in Outlook 2007 without having to use advanced search.
I will post back any progress I make with my ticket...
What ended up being the issue for us was there was a custom view called "event" on a bunch of our users calendars, and the even was filtering for only events that were "All day" events... No idea why it was on the machines after the upgrade to 2013... but b/c that was a setting that carried from the users mailbox to any machine in 2013, we were only seeing it on Office 2013 machines and not when they logged into a machine with Outlook 2007 on it.