I think that would be a long uphill battle with little chance of winning. Basically he would have to prove that the previous owners knew about the mold and did not disclose it.
I think the easier thing to fight here would be that there was a flood that the owners did not disclose. Clearly miamicanes didn't know about the flood, but obviously it happened. Unless the people miamicanes bought the house from only had it for a short time and the flood happened before they bought it, I think it would be pretty cut and dry to fight this. And obviously if he had known about a flood he might have done further testing for mold or reconsidered his decision to purchase.
Clearly mold located behind a wall - especially when the wall tests dry with a mosture meter - isn't going to be found by a home inspector, nor would (or should) any court hold an inspector liable for damages if they did not find the mold.
I don't think anyone disagrees with that, but if you look in the first few pictures posted here looks pretty clear that there is some mold damage on the paint on the outside of the wall. I would hope than an inspector who knew what he was doing would have been able to identify that and suggest that it might be something to look into further.
Also, miamicanes stated that there was reasonably obvious flood damage... swelling on the bottoms of the cabinets... stains on the walls, etc. Again, I'd think an inspector would be able to spot something like that and mention it in his report.
Obviously the decision to attempt to take legal action is up to miamicanes and I certainly wouldn't fault him no matter which decision he makes. I'm not normally one to just run off and sue someone simply because you can, but in this case, even if miamicanes does the work himself this is still going to be a significant time and money investment and I really think that some of that could be legally and rightfully recovered from the inspector and/or previous owners.