Advice on 'Recovered' Bike

Things that would help your case:

• Have an original bill of sale including the frame number and your name
  
• Have reported to police a "theft by unknown" of that bike with the frame number
  
  

I.e. if you can prove that it once belonged to you, and you can also show that you reported it as stolen then i don't see any reason they could have not to release it to you.