So that you return in time and find Arrav and RS gold explain to him your own situation. Then he tells you that he cant surrender the sheild to someone like you. ("a weakling" he predicts you because he is like level 300. Then you say you will help him stop the invasion if he allows you to maintain the sheild later. (in all this you never stopped to think what might happen to the upcoming!?) Arrav provides you the defense and you return. But when you arrive, there is not any more a scientist.
The device is still there however you are standing in the middle of no-were, (in which draynor use to be) so that you go to varrock. When you get there it is totally different. Rather than RuneScape taxpayers there are zombies and hob-goblins. They see you as meals and (depending on which level you're ) attack you. So you visit the Museum and its not there. Then a normal person comes out of cheap RuneScape gold a basement in the building you're in (you think its the museum) and requires you below floor level.