It's just a GUI issue, "Counterwallet addresses cannot "disappear" because they are cryptographically tied to the wallet which has a 1-to-1 relationship to the pass-phrase."
Just use the "Create Regular Address" option and create new addresses till the old one appears again. Here's the support link: http://support.counterparty.io/support/solutions/articles/5000008019-my-fourth-fifth-address-in-counterwallet-disappeared-
It’s just an issue with the graphical user interface (GUI) and what is shown to the user may not tell the whole story. In this case, many addresses can be generated from the seed that creates your Counterwallet and they will be created the same way each time if the GUI should happen not to show them properly.