K, that was good
What if?
GF not interested in bike anymore. Stages a theft story to throw BF off so she can Pocket the cash from a bike he paid for. OP not getting return calls from police, no way to know what's really going on. GF reports bike stolen, later calls and cancels report saying she forget a "friend" had a key and borrowed the bike. Really, to take a bike by van you need two people. Who would waste their time on a ruckus, how would you motivate a buddy to help with this waste of their time. If I were the op I would find out more about this friend and why she's busy on her birthday.