Not speculating on what went wrong ... just making note of the meaning of the term "kill rights
In EVE - when a player blows up your ship - if you don't shoot back - you have kill rights against them for 30 days. Meaning - that you can attack them anywhere without fear of Concord. But you can only do that one time.
Thus, someone comes along in a Vengeance and blows you up. If you ever catch them in an industrial you can freely gank them one time. Of course if you catch then in their Vengeance you can attack them too ... you just may have more trouble killing them than if they were in an industrial.
Any time you get blown up and don't know why - one of the first things to check is the Reset tab in your Esc menu. Look at the things that you can "reset". If you've turned off something that would have given you a warning - this is where you can turn it back on - but the mere presence of that reset button - indicates that this warning had somehow gotten turned off.