Try as best you can not to worry about the lawyer. That is just obnoxious in my opinion. If a note from the DOCTOR isn't good enough for them then tell them they will foot the bill for a fortune teller to find the exact date and time you will return to work. Maybe someone to read your tea leaves or something.

And in the meantime, them stressing you out about it isn't helping your recovery process any.

Drop all thoughts of them and focus on your doctor and your own well-being.