Amazon OpenSearch Service - loss of data due to service restart

Hi, we are using Amazon OpenSearch Service for application logs with a single node and suffered loss of data.

The service became unavailable for ~15 minutes, until it restarted without any previous data and different/unknown admin credentials (which we had to change). We suffered loss of all logs which were stored in the OpenSearch service. My question is why did the service not restart with the original disk and did not load the data back? Is it possible to get to the lost data? And how to avoid future loss of data if such an event occurs again? Possibly without running the OpenSearch in a cluster mode with three or more nodes due to the unwanted cost increase.

Overview of the OpenSearch service instance: Instance type: m4.large.search Number of nodes:** 1** EBS volume type: General Purpose (SSD) - gp2 (512 GiB) Before the crash of the instance the volume was less than 45 % full, so we know that the disk space didn't cause the crash.

Thanks for any suggestions!