It was your shields modifications for starters , they fall very easy to reverb mines. Also fletchett launchers could have played a roll in this , if you were being fired upon, they are somewhat discreet because of the minimal damage they do to your shields and hull when module targeting. One more thing , the warning system for torps can be easily handled through various techniques , but I wont be giving out those secrets.
mmm...ok, any tips for the shield mods?