Wow... that's a freaking theft... The wallet was online I assume?
Electrum - dropbox was compromised (with plain txt for the pwd, I know I know..)You are shitting me .. you kept >1000BTC and you had a txt file with your password on a dropbox.
I wish I can track those thieves but perhaps this will be not possible for me.
Kind regards.
PS. Lesson for newbies and not only: Never store your password anywhere else than in your brain OR write it down on a piece of a paper and keep it SAFE in a place that is known only for you! you can even slice it and keep in different places
Change your password from time to time
...