The question i would ask you is that was the phone locked when you left it, if not then there is nothing to worry about.

awwwwwwwwwwwwwwwwwwwwww

cococandy:
Are you sure you're not lying @OP.

A two month old can't hold a galaxy s3 upright.
Even if she took the pic by mistake it wouldn't be straight because her muscle is not string enough to hold an s3 straight.

True

i don't believe for a second that 2 m/o baby took a selfie. by this age she can not grab things, or lift such a thing like a smartphone (you said that she played with it)- the muscles are not developed. even if the phone was set to do selfie, the probability that she will touch the right place on the screen is really low. so try another story this is a fairy-tale.