Even after the dogs dispersed, the interloper remained in motionless mode for some time. Opossums sort of go unconscious when they Play Possum, though this fellow apparently did not go full swoon.
After the dogs came back in the house, the intruder was left alone for a while. He moved to leave. First he tried to climb the fence. That proved too strenuous. He then moved to the gate, which presumably he squeezed under, for all of a sudden this phlegmatic interloper was gone.