I completely cleaned out a tank, drained it, removed the substrate after the tank sat a week with a few inches of icky water, dried that tank and it sat a few days completely dry.
Started to set up the tank again with new substrate and filled it with water, suddenly a shrimp was swimming around in that tank,
The litter bugger must have lived in a few inches of residue in the internal filter cabinet and have been torpedo's out when I turned everything back on.