Got robbed by a person I know

so these past few months ive had an extraordinary streak of extremely bad luck and today I just so happened to find my piggy bank with over 500 euro missing entirely that money was given for me by my brother for, several reasons, so my parents agreed that they wouldn't take any from me as that would just make things worse for all of us here's the thing, there was this mechanic that my dad told to come for some repairs in my room and at the time I was away so I didn't know what he was doing there all alone, my piggy bank was located under my desk and since my dad recalled seeing him moving my desk, the piggy bank started making metallic sounds he obviously heard it and snagged everything while my dad was on the couch, not looking. hes the only person that has ever stepped in our house except for my parents and my brother by process of elimination it is definitely him, my brother is obviously excluded because he gave me that money and so are my parents because there's no reason for them to do so, or if they do they at least only take really small amounts, then tell me and promise to repay me what do I do here? if my brother learns I lost his money (500 euro is a fuck ton) things won't end well my parents are really pissed too and they're trying to think of something but for the most part we're clueless Im in desperate need of help as that money could easily be used up by the guy fast

there's a problem, my dad says that wont help at all since they have no way of knowing if the stolen money is even ours in the first place which is kinda true honestly, never thought about it like that should I still have a go at it myself? I have a friend whose dad is a police man

uh damnit, I forgot to mention my dad personally talked to the mechanic and even tried blackmailing him but he swore he never took anything, so that's something to think about too