Hi there!
There are a couple of reasons data can come up missing after reinstalling.
Removing the application in any way besides dragging its icon from the Applications folder invites complete data loss, because third-party tools that uninstall applications can do a very thorough job of removing all of CheckBook's support files, including its default document. The only fallback in this situation is Time Machine or another backup solution. We can help restore your data if you send a message to
support@splasm.com.
Installing CheckBook when CheckBook Pro was originally installed, or the other way around, can make it appear that data is missing because each application doesn't know where the other stores its data, so your regular document needs to be opened manually the first time. We can help locate your document if you send a message to
support@splasm.com.
As long as only the application icon was dragged to the Trash and the proper application was reinstalled, everything should appear exactly as it was before. The only thing changing during the reinstallation is the Mac App Store receipt - the actual application is identical. If your data appears to be missing we can help determine what happened if you send a message to
support@splasm.com.
I'm sure we can help out there. Hope to hear from you soon!