Slip By Meaning

(idiomatic, intransitive) to pass without having been taken advantage of.

Example: 2011 June 28, Piers Newbery, “Wimbledon 2011: Sabine Lisicki beats Marion Bartoli”[1], BBC Sport:
  She held her nerve after failing to serve out the match at the first attempt, seeing three match points slip by in a nervous service game at 6-4 5-4 and recovering from losing the tie-break to dominate the decider.
to go unnoticed
  The children managed to slip by when the patroller was looking away.
  The children slipped by the patroller.