Does any of your collaboration with this coworker involve using e-mail? If so, bcc your immediate supervisor.

As far as speaking to your boss, you never know if perhaps there's already some semblance of knowing there's problems with various employees.

Arming yourself with a copy of your own work is arming yourself with facts, which can usually disarm any sidestepping.

Saboteurs can usually out themselves in a matter of time, because if you're doing your part it's only a matter of time before the weak link shows.

Why would deleting your part be remotely acceptable? I hope there's something in writing for your sake.