Frankly I would worry about that with any third party that holds my data. There are a few Bitwarden exporters on Github that also account for attachments (something the builtin exporter doesn't for some reason).
BW synchronizes all your data on each client... if you logged in before, and your server goes down, you can still log in to a recent client, it just won't be able to update
you could recover from that
No way to export from the client though, so you would have to recover the server unless you previously made backups with the export feature.