civicrm_participant_get() doesn't query by participant_id

The wiki and code documentation indicates that civicrm_participant_get() should return a result based on a participant_id parameter. Instead it returns an error with all rows.

In api/v2/Participant.php, civicrm_participant_get() is a wrapper around civicrm_participant_search(). Looking at line ~187, it seems $query->query() never generates the where clause. Chatted with eileen on IRC and thought it looks like it could be a unique field vs table field issue - ie. 'id' vs 'participant_id'.

Calling civicrm_participant_search() with the param participant_id also returns all rows. Happy to help debug this but getting a bit lost in the query.