There is a distinction. Usually statistical mechanics means the ensemble theory and partition functions that connects microscopic systems to macroscopic ones from material point of views. However, statistical physics is a bit more generic, for example complex networks may not use ensemble theory or partition functions and could use only statistics on the network, such as average neighbourhood or similar.
What I'm getting from this discussion is that we use Statistical Physics to refer to anything covered by Statistical Physics AND Statistical Mechanics, while we use Statistical Mechanics in a narrower context, but it is also possible that some use SM loosely.
