Yes, pans are important. Being the #1 major concern, maybe. But there are so many different things to check, I’m thinking #1 major concern is to assure there is an air handler.
Because there is no pan, you made the right call pointing it out no matter how you phrased it. What you don’t know is if the inspector the client used did report the lack of a pan and the client just didn’t bother reading the report. Or was told about it and didn’t bother giving it any further thought.
I had a client call me to do another inspection for them and she requested that I check the GFCI outlets in the bathroom to assure they are working properly since they weren’t working properly at the 1st house I inspected for them. I looked up the old report and there it was under the bathrooms,“GFCI outlets not working properly…”.