Not to worry, InventoryLab autosaves each batch that is created within our system.
1. To restore a batch go to List>Closed Batches
2. Click on the batch you want to restore, the most recent batch will be at the top
3. Once you are in the batch, click on restore in the upper right hand corner
4. Click Just Restore
Select Just Restore and your new batch will appear on the List>List & Prep page.
If you want to restore a batch but only want to do this for certain items in the batch, or you want to restore the batch but change the box content settings, Creating a New Batch from a Closed Batch shows you how.