So, you catch a 'thief'...

I'd phone 999 anyway, cos they are duty bound to record it and act upon it....

phoning 999 if it's not an emergency is

1. pointless as it would only be treated as a non emergency call anyway
   
2. abusing the system as a 'real' emergency may be waiting to get through
   
3. pointless again as all calls 999 or not are recorded