I had lost a yo-yo Loach once.. I couldn't figure out where he went. I had swapped some tanks around, and moved my community tank out of the 45g that had an undergravel filter.
Well apparantly when I was moving my community tank, the powerhead on the UGF had fallen off and the yo-yo Loach darted down the tube when I wasn't looking. I had presumed him dead once I couldn't find him, figured he had gotten eaten. I moved my Buttikoferi in the 45g and had himo there for about 6 months.. I left the UGF in place, but just capped off the uplift tubes. Then one day during feeding time, all of a suddon, the Yo-Yo loach popped out from UNDER THE GRAVEL. It was the most amazing sight I had ever seen.. I thought it was buried all this time, but apparantly it was living off the detritus in the UGF.. It must of felt food and 'blasted' its way up through the substrate! Resiliant lil buggers!