LOCAL_ONE and QUORUM produce different results

I'm connecting to Cassandra DB via IntelliJ Data Source and run an ad-hoc query. We have this DB in multiple data centers. My connection string includes just a single node IP. With the same query and the same URL (connection string) I got different results (more returned rows) when I switched from LOCAL_ONE (apparently the default) to QUORUM. Apparently we have a replication problem. Based on the info I presented so far, is it possible to determine whether the discrepancy is between nodes is the same data center or between data centers?