I disagree with your analysis, but the details of why I disagree would be spoilers.

But I can only make inferences on what you've told me. If there's a factor that throws off the general inferences you can make from a salesman's clientele, you can't fault me for not using it. It's like you're trying to say:

"This dude was born in the US. He's 50 years old. Can he speak English?" -> Yeah, probably. -> "Haha! No, he can't! I didn't tell you he was abducted to Cambodia as an infant and grew up there!"

Anyway, the next step is to estimate what fraction of salesman with the same clientele composition have not had their clients die and see how atypical he is. Plus, his sales record would have to start from early in his career, or else his clients fall mostly within recent sales, a time span in which people normally don't die anyway.