I placed a text ad on the site and allocated some credits. I was watching it each time I logged in so I knew when to add more credits. Since I purchased 150,000 I had only allocated 2500 to it. Today when I logged in it had completely vanished from the advertising panel. I was not sure what to do so I sent a support ticket. Then I decided to try something else. I placed a text ad again. And it let me! Then I had access to the credits that were purchased. So I guess once your text ad reaches completion of the allocated hits it simply goes away and then you must place another one. 

This works for me, becuause I decided to change to a new ad anyways. Just thought I should share in case others find this situation confusing like I did.