If you are using the console, you should be able to run the following Plastic commamnd:
cm undelete --help
Undeletes an item using a specific revision.
cm undelete revspec path
revspec Specification of the revision whose contents will
be loaded in the workspace.
path Restore path.
The item to undelete should not be already loaded in the workspace.
The undelete operation is not supported for xlinks.
cm undelete revid:756 C:\mywks\src\foo.c
cm undelete itemid:68#cs:2 C:\mywks\dir\myfile.pdf
cm undelete serverpath:/src#br:/main C:\mywks\Dir