Contrary to popular belief, brief exposure to a vacuum does not result in you instantly exploding. Any water exposed to the vacuum would begin to boil due to the drop in pressure (and subsequent lowering of the boiling point of water to a point where your body temperature is hot enough to boil it). However, your tissue (skin, blood vessels) is elastic and porous enough to swell and accommodate the expansion from evaporation and some fluids would remain liquid. The miner could survive his brief exposure, especially since his suit would likely be pressurized enough to avoid full body exposure, and with a less than rapid depressurization of the face mask.
The term "sheep dip" was originally for an insecticide liquid applied to sheep, but here it refers to a spy building up a cover story before infiltrating somewhere.