Mouse Hole Stopped Working After Placing Trap!

when the trap was placed..the game lagged for a moment and it was as if the trap vanished into the wall.  The point I was trying to make is...that I opened an earlier saved game after placing that trap (a save where the mouse was running in and out), but the mouse was no longer running in and out.  Why would the placing of the trap affect a previously saved game?  In addition...when exiting the game that I placed the trap in, I did not save that game, but rather, opened an earlier saved game.  The mouse just stopped working.  I am going to wait...as the mouse may appear at a later time like the previous poster stated.  It may not be a bug...but it is weird that the placing of the trap affected all previously saved games.