Is it possible to find the owner of the adress 15puCD3bGbTcX9krmDfPKicoMhAMC4njvh ?
That's very unlikely.
Is it possible that it was a bug or a mistake ?
The transaction was made a week ago and you said that you only opened the wallet today. So there is no way the transaction was made from your computer (so, not bug or mistake). This probably means that you either:
a. At some point downloaded a fake Electrum version from a phising website (the only legit website is
electrum.org);
b. Had a malware in your computer which compromized your wallet;
The hacker somehow got your wallet file/seed, restored the wallet and sent the coins to his address.