I believe SQL Server doesn't store this information in its system tables. You can see who owns the procedure, but that is not necessarily the same as who created or last modified the procedure.
You might be able to find out through the default trace (the your data folder for .trc files), but this information is only kept for a few files(5 files and ~100MB each).
There is a Standard Report that will show you the schema change information that comes from the default trace. This simplifies things somewhat for you. (Unless you have the default trace turned off.)
Reports --> Standard Reports --> Schema Changes History.