The mixers keep a ledger outside the blockchain, so no—and a well written one wouldn't store any logs. You could possibly know that someone used a mixer but you

The mixers keep a ledger outside the blockchain, so no—and a well written one wouldn't store any logs. You could possibly know that someone used a mixer but you wouldn't be able to track from the blockchain where the money came from. It could've come from 1000s of other transactions all with different amounts—none that would trace back to the source funds wallet.