Lost my phone without GPS & data plan on I have checked other questions on the site and I think my question is not completely duplicate

I have lost my OnePlus 2; it is in different country (Indonesia) and I have no way to contact any authority over there. Fortunately, I had local SIM in that which is ringing once a while. 

As, my phone contains some very personal images, so, I opted to erase content via Google Android Device Manager. Now, my questions are:


Is it possible to unlock phone with any software? As android manager says that data will be wiped out as soon as my phone will be connected to internet. But, I am worried if it possible for anyone to unlock my phone. (I had 3*3 pattern lock).
What else precaution I can take care to avoid any personal data loss? I am mostly worried about pictures.
Question 1

Theoretically not possible for an ordinary thief - it is enough of a deterrence. If the thief stole it from you, with an express international of gaining access to that data and he has sophisticated tools at his disposal, then you need to be worried. But going by your description, it is unlikely. There are also other factors involved, which you can see in this SE.Security question Is Android's Password Screen Lock Enough Data Theft Protection?, which explains in detail how it is possible for a determined person

In security parlance Physical possession is ownership is often said, but that's the worst case scenario

Question 2

Sorry to say but there is nothing you can do, till the thief chimed to internet and device is wiped.