This article will walk you through how to find all of your campaigns. Make sure you are in the correct Advertiser from your Advertiser dropdown menu (top right of dashboard).
Click on Campaigns in the Dashboard, the default shows the campaigns created in the last 7 days (highlighted in Green).
Click on All to see all of your campaigns for the selected Advertiser OR type in the Search field.
If your campaign still doesn't appear, it may have been Archived - select from the "Show" dropdown menu to see Archived Campaigns: