What do I do if the sitter lied about having a dog and said dog attacked mine?

You should call Rover's emergency team, they should be able to go over the options and make sure that the sitter is followed up with. I am so sorry to hear about your dog and I hope everything is ok now! The emergency number is 888-727-1140.

Definitely contact Rover's Trust & Safety Team. If this stay was booked on Rover, you'll need to submit & have your vet submit some info. in order to receive medical reimbursement and possible refund. Then Rover can look into this sitter's profile too.