Re-enabling replication after multiple host failure

I have been successfully running a 3-member replicaset on 3 separate VMs in 2 locations.

My mongo_uri was of the form: mongoldb://username:password@member0.host.com:27017,member1.host.com:27017,member2.host.com:27017/?replicaSet=rs_name

This has worked perfectly for 8+ months.

On Tuesday however the host where 2 VMs are running, had a data center issue. As a result (I can’t really deduce the order of things), my primary became a secondary and was unable to elect itself to primary again.

As the situation at the data center lasted beyond reasonable times, I decided to restart my primary member as a standalone node.

Basically, going from:

mongo:
    image: mongo:latest
    container_name: mongo_mini
    restart: always
    command: --replSet rs2 --keyFile /kk/keyFile

to:

mongo:
    image: mongo:latest
    container_name: mongo_mini
    restart: always
    #command: --replSet rs2 --keyFile /kk/keyFile

This resulted in this member starting up again and my services being able to access the db again (after telling them to look for the standalone host).

My question:
The data center is up and running again, 1 VM had to be re-created and the other still has the replication data.

My hope is that I can revert the change for my current standalone host and restart again with the --replSet command enabled, but would that work?

The new VM will start in STARTUP2 mode syncing and hopefully the surviving VM will pick up replication where it stopped 2 days ago?

Happy to hear your thoughts.