Hi Jessica,
Yes - unfortunately we don't yet have the infrastructure to deliver a collaborative editing experience yet....but we have it on our long term roadmap to address. Implementing something like this makes some larger architectural changes to how items are stored and how updates are processed so it wasn't something we could do quickly.
Apologies if you have had some data loss....it's something we know is very frustrating. I recommend you keep your work to one tab to avoid saving something stale for now. We're also considering some versioning approaches that may mitigate this as well.
Apologies I don't have a better answer for you today!