Hmm, now that’s very interesting, Steve! I was in Pompeii last summer and I don’t seem to remember this beautiful painting. I’m sad I missed it. At any rate, you’re right about one thing—it’s well known that the Romans had centuries of indirect contact with China, through third and fourth parties.
As I mention in the article, Chinese silk was so popular in Rome that the senate tried to outlaw it in 14 CE. Imperial Roman coins have even turned up in Japan! It’s also true that the Romans had numerous trading posts on the west coast of India, which helped their goods and coins bypass Persia.
What’s much less clear, though, is whether Roman and Chinese diplomats ever had any direct contact on each others’ native soil. Most of the land routes to China from the west coast of India — or vice versa — crossed through Bactria, which was Persian (and/or Kushan) territory; unless Chinese or Roman sailors wanted to sail all the way around the Cape of India, which there’s no clear evidence they ever did.
As for whether Roman and Chinese traders ever met up in India — well, as far as I know, there’s no direct proof of that either. But I don’t find it at all implausible, and the history geek in me really wants to believe it happened.