Is there anyway a thief can get into a locked iPhone?

:( someone stole my phone yesterday. It was one of my so called friends however I notify the police, apple and my phone company.

The iPhone can plug up to a computer - of course there are ways to break into it. Whether they are smart enough to figure it out - I don't know.

You might can disable the phone service so the thief can't call or text anyone.

Depends on how "tech-savy" the person is. It would need to be a person who literally trains to hack into phones, no normal person could do it. HOWEVER you can plug it into a computer and get all the songs, contacts, so forth of it. But no they can't use the physical phone, rarely will you encounter someone who knows how to hack a stolen phone who is on the streets, someone of that mental ability is normally working a government job.

You would need some kind of software to reset it to factory defaults. It's available but I have no idea how to access it. Otherwise whoever took it is just gonna be stuck with a locked iPhone and no way around its security. Accept breaking it, it should be safe

Its actually quite easy to reformat the phone, but to 'get into it' as in view all the data etc. It would be a hard and long process, as there's no 'backdoors' into getting through the unlock screen without the pin.
There may be bugs, and depending on the phone OS a glitch may allow the person to bypass the code and view all your data.

Best to notify the police, tell them who you think it is

Yes, it is possible.iLostFinder seems useful, I will try later.