Well, there's no way of cracking SA-MP's password.
Your "friend" could've seen you typing the password in and taking out all your cash without your knowledge - your fault if so..
Or you've got some sorta of keylogger on your computer and someone sniffed the password..
Anyway, managers are able to check transactions logs and they can tell you how did the money vanished.
PRO-TIPS:
> Never share your passwords..
> Use "hardcore" passwords, like "ds!<2012isafter2011>!sd"
Good luck anyway