Death Knell - S7-E16
Corrected entry: After the G'ould attack on the Alpha site a malp is sent through the Stargate which is now on its side. The malp is therefore stuck at the bottom of the pit created by the incoming wormhole it travelled through. When SG-1 then travel to the alpha site and appear in the "perfect foxhole" the malp has magically disappeared. (00:08:00)
Correction: The malp has not "magically disappeared". It was destroyed by the unstable vortex created by the re-activating Stargate.