Home Robbery

So this morning before work I walked outside to my car and noticed my door unlocked....I forgot that I didn't lock my doors after I got home last night ....my cousins girlfriend came over and was parked behind my car that night and I noticed my wallet was missing and I didn't have any money because I dot leave money in my car...they took my booksack and threw it out in the canal...I'm just wondering who on earth would do this my family members ,friend or was it really someone who I didn't know robbing me late at night? Who do you all think it may have been?