A senior data engineer executed a VACUUM orders RETAIN 0 HOURS command on the orders Delta table. During execution, a junior data engineer, unaware of the ongoing task, began ingesting data from a source table with non-zero records into the same orders Delta table. Post-ingestion, the junior engineer found the table empty without any error messages, only to later discover that an insert operation was performed in parallel with the vacuum. The table's history showed only VACUUM and INSERT actions. What could be the reason for this occurrence?