Please describe how the WBS was overwritten, was it a transfer from a PS Version?
In CJ02 you should be able to type back in the WBS and description as desired in the operative version. The short id will adopt the WBS you enter.
The WBS number, Description and short Id are all basically text descriptions, the way SAP identifies WBS elements is by the object number, that PR.... number. What you see as a WBS number is not what is actually stored in the tables, it goes through a Conversion Exit to display it to you. The WBS coding mask is not really stored in the tables, it is overlayed when it is displayed.
In SE16N click on Extras, Change Settings, then check Output without Conversion Exit. Look at your WBS in PRPS and you will the "real" values.