Disappearing Data In Split Database - Access 2007

I work with an Access 2007 database that I split into a front end and back end. The back end holds all of the tables and the front end holds the queries, forms and reports. It is also a multi-user database, in that we have 14 people having access to the same back end. Each of the 14 people have their own front end. I have one main table in the back end listing clients and their individual ID numbers. That table has a One to Many relationship with several other tables, such as Case Notes and Authorizations, to name a couple.

Here's one of my problems: Sometimes data that is entered by a user will disappear.

Example 1: User creates a new record in the Authorizations form. Sometimes it is created by duplicating an existing record, sometimes it is completely new. User then prints a report from that new record, which looks like it has been saved. A couple minutes later, or a couple hours later, or maybe even the next day, user goes back into the database and cannot find the record that was previously created. At that time I look in the back end and cannot find the record either.

Example 2: User creates a new record in the Case Notes form on Day 1. These are always completely new records. User returns to the database on Day 2 and the new record sometimes does not show up in the form or in the back end table.

I cannot MAKE these things happen and they are sporadic, which makes it hard to diagnose, but why this was happening or if there was a way to retrieve the lost data.