What if all nodes stopped working
Without nodes in a network, there is no network.

In the situation where the 1000 nodes (or even a subset of them) suddenly came back online, the network would simply continue where it left off.

In the situation where all nodes went offline, and all existing data was lost, then the network would begin from scratch with a new blockchain whenever the nodes came back online.

Keep in mind that data loss of the blockchain is highly unlikely.  Since there are so many copies, it would take a fairly catastrophic event to destroy all copies.  In all seriousness, it's more likely that all members of the human race will be destroyed than it is for all copies of the blockchain to be destroyed.  Assuming that a copy exists, the network can always be restarted from one or more backups, and conflicting backups will follow the consensus algorithm to determine which version is more "correct".

Bitcoin is extremely resilient.