This tip is ill-timed given your current circumstance, but we export all columns of our full Marketo database each month and it has helped us restore several records that were corrupted.
If you have a limited number of Lead Status values, you can create a smart list with the Data Value Changed filter and look for changes from each Lead Status value to "unsubscribe" on the day the change was made. Then select all of the leads in the smart list and use the Change Data Value flow action to change the value back to the previous value.