Unsecured wireless internet?

I was connecting to someones wireless network, I didn't know who this person was, I also did not know that I could actually do this... So basically what I did was I click show other networks or signals or whatever around me and see a bunch so I see this caution symbol and it says "Unsecured" so I click it and somehow it auto connected to that netowrk for 3 days, every time I turned on my laptop it would connect to that network I later found out today I was not connected to my network(I was kind of confused), as soon as I found out I could get into serious trouble for it I stopped immediately, and now I just want to know if I used there wireless internet for gaming/search's can they still see it even after I went off their network? or did it just disappear. 'Cause I don't plan on ever doing this again :/