Breaking through passcode?

[reetcher]

Someone recently, at a party, got a hold of my iPhone 4s with ios7 and was able to get through my passcode and make a phone call (2 actually). The phone had not been used for well over thirty minutes(in zippered jacket out of my hands) so the passcode should of been engaged (I have it set for 15minutes) This was not an accident the phone numbers are there along with the fact that the passcode was set. I've called the numbers and it is obvious who did this and when now I'm curious why, how and what should I do to protect my phone's info or email accounts?

My question is how did they do this? And second can they be receiving any future info, updated contacts, emails, etc? What should I be aware of?

Thanks for any insights or advice

 

[SandboxGeneral]

It could be that whomever did it, knew some information about you which led them to guessing correctly. Or, that they watched you enter the passcode and knew it that way. Or, it could be, that the 15 minutes hadn't elapsed like you think it did, and they just swiped to enter.

 

[C DM]

Various previous versions of iOS had some glitches that allowed people to bypass at least some parts of the phone being locked and give them access to contacts or photos or ability to make a call. Potentially could have been something related to that.