I've just quickly hacked together an sbt plugin to suggest dependencies that are missing from your sbt build files, given imports that can't be found:
https://github.com/greenrd/sbt-autodepsIt's not terribly useful at the moment, but I've added some TODOs to the issue tracker to indicate how I think it could be made more helpful.
I suppose a slight downside of using this plugin is you might then opt for the easy option of using the same version of a dependency that you (or someone else) used in a previous project, without checking to see if a newer version of the dependency has been released since then. But taking into account concerns about new versions breaking things and so on, that might actually be considered a good thing in some cases!