Hi Eddy,
Custom data sources can be visibe RSA6 only, not RSA5. RSA5 its SAP Defined data source only.
Try to check RSA6, select your data, recheck all the fields. there might be there.
if not then you need recheck your steps how you added.
Please check below discussion. might be useful.
http://scn.sap.com/message/14053153
Thanks