Problems adding a component in Eagle CAD
@Angs @Tom Carpenter - So it seems that the device was never made - I had a symbol which had been procured from somewhere, but it wasn't linked to a package and wasn't a device in the library (hence why it never came up). So I've made the part and it now appears in the library. Thanks for all your suggestions and time - they are things I will definitely keep in mind when I'm using this software