Should Zakat be redistributed if it was mistakenly given to a mosque, or is the sin absolved due to lack of knowledge?

It is not permissible to disburse Zakat except to the eight categories mentioned in Surah At-Tawbah (verse 60). If it is disbursed to those who are not entitled to it, then it is obligatory to re-disburse it to those who are entitled to it.