Find my Iphone didn´t work! Help!

Hi guys I´ve got stolen the IPhone 5c with all my data. I used the Find my Ihpone feature and it did found my IPhone at first but when I went to check my e-mail to see where it was I realized that I have another e-mail reseting my pasword as they went like "I forgot my Id or pasword" . Then of course I whent again to my Icoud account and find out that my IPhone was disconnected, Find my IPhone was disable. Now my email account to reset my pasword was connected by gmail App and you could have acces from my IPhone, I think they had acces to my e-mail, is that posible? I never checked my IPhone blocked so I don´t know what can or can´t you do with it.

Í´m worried becouse I had my data there, photos of family, and accounts configured to have acces to my e-mails accounts, FB, etc. If I change my paswords on my computer, my IPhone will be able to enter my accounts even I change the passwords?

Thanks for all your help

Regards, Pedro.