I had my dagger disappear the first time too. Probably I dropped it on the other side of the wall. Make sure you know where to put the dagger, so before taking the dagger out from inventory, look for a hand where you are going to place the dagger.
Edit: Yes, the ruins need to be touch in a certain order. Look at wolfie's site for exact information.
http://wiz8.web1000.com/RetroMaps.html
[ 10-21-2002, 01:12 AM: Message edited by: el_kalkylus ]