Mine's done that too.  They go where the alu body panel joins onto the steel behind it thanks to every Landy owner's favourite electrochemical reaction.  :roll: 
Having used a stupidly strong glue to put one of my doorskins back on, I'm tempted to try the same thing again on that panel.  If you get a decent thickness of glue, then the two bits should be electrically insulated from each other which will hopefully stop the alu rotting away again.