What did the trace files tell you? Look in the dump directories on the remote server. If you're not sure of their location, launch sql*plus and so SHOW PARAMETERS DUMP_DEST as this will show all directories used to store that database's trace files.
Even though you're interfacing with database 1 via the OCI layer, your query is hitting database 2 via the OPI layer. There is a separate process handling your request; it is not being processed by your server process. I would therefore not limit your search to log and trace files stored locally.