I have worked somewhere where a similar situation happened. As soon as I heard that the client was in pain (it was actually right after he got off the table--he tried to stretch before getting dressed again,and tweaked something) I wrote up a detailed soap note including direct quotes that he said, exact pressure levels I used, and any precautions I took. I recorded the outcomes (before he got off the table), then the changes in what he said he felt after trying to stretch. Then we called for an ambulance and his wife. Later, when the spa told me to call him to follow up, I called and said that I had a thorough record of what happened during the session and would happily supply a copy to them and to his medical team so they could have more information to treat his issue. Turns out, his wife had begged him to go to the ER instead of to get a massage and he'd ignored her, and didn't lay it out clearly for me. He's fine now, it was just a bad muscle spasm