I've had this happen randomly two occasions now... On a random build, a scene will write its files as ActorEvents_xx.hx, ActorEvents_xx.design, and write the scene properties in list.xml as an actor. The scene XX.scn file will stay until you close and reopen stencyl. The first time this happened it overwrote an actor with the same number (scene35 overwrote actor35). This time I got lucky and the scene number was between actor numbers.
The exact scenario: Scene 36 files were erased, and became ActorEvents_36.hx, and ActorEvents_36.design. The headers of the files had actor methods, but the rest of the logic was the original scene logic. List.xml had actor properties for the scene (<snippet actorid="36" attachedevent="true" class="scripts.ActorEvents_36" classname="scripts.ActorEvents_36" desc="Actor Specific Events", etc.)
I managed to hack everything back together as a scene with text edits, but this is really concerning moving forward.