Old Mapping in Index ReAppeared

We observed a strange issue in Elastic Search Cluster. We deleted a mapping and created a new mapping and then loaded all the data using one shot river.
Search was working as expected, however the old mapping in the index reappeared out of no where.

Has any one faced a similar issue and how can we ensure the old mapping is not cached in Elastic Search.

Check that it isn't a template as well?

This would suggest you are using an old version of ES, so upgrading would be recommended too.