I'm a woman and if that was my boyfriend, I'd dump that him and FAST. He has no morals and ethics! He's also a real crook! What he did is called "petit larceny"!! If he'll steal from a complete stranger, what makes you think he won't steal from you one day? If he'll lie, cheat or steal from other people, he'll lie cheat and steal from you!

DUMP HIM! And call the cops. (If you don't want to call the cops, that's fine. Leave a note on the bike telling the owner who stole it and leave your boyfriend's name, number and address.)