From your original posts, I thought you broke up "3 years" ago. There is a big difference between 3 years and 3 weeks
. I am guessing that you left the laptop 3 years ago, but were still in this relationship.
I still can't answer your question unequivocally (and I am a software engineer). There is too much information missing to prove beyond a reasonable doubt that he violated your privacy, there are a great number of things that might have happened. Some browsers save passwords, it is certainly possible that he unintentionally pressed "enter" to generate that notification.
I still don't think it matters... unless you are thinking about getting back together with him. If you could prove that he violated your privacy, what would you do about it anyway? It is not like you can break up with him.