I have investigated every USS in game but I even did a two week solid tour of duty looking for cans, with hardly any luck at all, in all different systems as well, my findings resulted in 97%b chance of material finds and 3% chance of cargo this is where the problem lays, not an even balance, i'm hoping frontier will change this.
Finding cargo was the only element when the game released since then it is rare thing to come across which is sad as the game is about trading, combat, exploring, not just materials all the time....