This encounter can be used during any travel through the Warp:
The explorers vessel suddenly drops dead out of the Warp into a Warp-Pocket.
In the middle of this pocket floats an ancient shipwreck, which has been damaged by warpstorms, radiation and impact from debris beyond recognition.
Closer examination of the wreck indicates, that it seems to be of human manufacturing - there might even be a faint signal or power source emanating from the command bridge.
The hull of the wreck has long been breached and the inner corridors of the vessel are filled with dead, withered corpses, floating around.
A visit to the command bridge reveals, that the bodies of the command crew are still on the bridge. The body of the commander of the ship might even still be on his command throne... the scene should strike the explorers with an eerie feeling of familiarity.
Terror (sanity points?!) should strike the explorers, when they finally realize, that they are currently standing on the wreck of their own ship and staring at their own frozen and partly decomposed bodies . This can be realized by either identifiying remains of unique personal equipment on the bodies (such as a unique signet-ring) or by discovering the explorers own dynasty-crest or ship name engraved on the bridge beyond a layer of ice and dust. At this point the explorators should be forced to leave the wreck in a rush, as the warp-pocket begins to collapse.
It should be up to the GM if this encounter is nothing more than a trickery of some entity of the Warp or a grim omen of future events...