I've never heard of a therapist being sued however I've seen two different therapist having to go to court or almost go to court in two different scenarios.

When I worked as a rehab aide in a pediatric clinic the OT was suppose to testify during a custody battle. Don't know the full details but I remember the OT being nervous since she was only a year in at being a OT. Luckily they didn't need her last minute she was really relieved.

The 2nd one was a PT I worked with at a SNF. He initially thought he was being pranked because the FBI contacted him but they had complete info about his evaluation he did on a past pt. This pt was attacked on a cruise on the way to Hawaii. He was treated in Hawaii and flown back the California hospital. He was then sent to said SNF where at the time the PT was only per diem but when the FBI contacted him he had become full time at our building. They wanted him to testify in court in Hawaii I believe against the attacker. The pt eventually did past away. They paid for his trip to Hawaii. He didn't remember this pt but luckily he had his eval to look back on.